JP2022118469A - Biomass gasification device - Google Patents

Abstract

To provide a device for heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace, wherein the device can be operated continuously without any trouble due to generation of clinker or tar, and can collectively use plant biomass of various plant types, parts, and sizes as a gasification target without concern about moisture content or the like.SOLUTION: The foregoing problem is solved by a biomass gasification device that heats plant biomass in a rotary kiln-type furnace, the device comprising: pyrolysis means for heating plant biomass at 800°C or less and discharging a pyrolysis gas; and tar component removal means for removing tar components from the pyrolysis gas at 650 to 780°C discharged from the pyrolysis means.SELECTED DRAWING: Figure 2

Description

The present invention relates to a plant biomass gasification apparatus performed at a predetermined heating temperature.

A large amount of branches and leaves are generated by mowing, pruning, etc. in the maintenance of forests, large-scale parks, slopes of highways, and the like. If these can be used as energy resources without being disposed of as waste, it would be desirable from the viewpoint of cost reduction for disposal and future prospects for global energy. However, when herbaceous plants are burned, potassium oxide and silica in the ash react with each other to generate a large amount of clinker. Moreover, although a fluidized bed furnace is often used as a gasification furnace, there is a problem in that char treatment is required, and gasification using a fluidized bed furnace is difficult. For this reason, branches, leaves, etc. generated by mowing, pruning, etc. have been disposed of as waste. Bamboo also has the same problem as herbaceous plants because it contains a large amount of silicon and potassium, making it difficult to use as an energy resource. As a result, the number of abandoned bamboo forests has increased. Due to the above circumstances, the development of a system that effectively utilizes herbaceous plants and bamboo as energy resources has been demanded all over the world.

In addition, in a device for biomass gasification of plants including herbs and bamboo, tar generated in the gasification process interferes with continuous operation.

In addition, plant biomass generated by mowing, selection, etc. includes a variety of plants, and plant parts such as leaves, stems, and roots also vary. Therefore, plant biomass generated by mowing, selection, etc. is a miscellaneous mixture of various water contents. When plant biomass is used as a raw material for a gasifier, measuring the moisture content of plant biomass and keeping it constant is one of the means for suppressing the generation of tar and clinker. The cost and time due to the increase was a problem.

Patent Document 1 describes a combustion apparatus using bamboo as a biomass fuel. In the invention described in Patent Document 1, in order to solve the problem of clinker generation when using bamboo as a fuel, the bark of cedar, cypress, etc. is mixed with bamboo and burned, and the ash in the bark is burned. Calcium oxide prevents the formation of clinker. In the device described in this document, there is no suggestion of the concept of preventing the generation of clinker by temperature control.

Patent Document 2 describes a biomass gas generator that reduces the generation of tar by including a step of injecting water into the generated gas. However, in the apparatus described in this document, the temperature of the generated gas is about 300°C and the tar does not vaporize, so the vaporized tar is condensed and recovered in a high temperature range of 650°C to 780°C. There is no suggestion of the idea that

Non-Patent Document 1 describes a system ( FIG. 5 ) in which biomass is chipped and heated in a pyrolysis furnace to be gasified as follows. Regarding the system called "new green recycling system by biomass gas power generation", there is the following description. “The system flow for biomass gas power generation is to dry biomass chips in a dryer, heat and steam them in a pyrolysis furnace, and decompose them into pyrolysis gas and char. Gas is purified by blowing washing circulating water on the soot.The final refined pyrolysis gas is sent to the generator and mixed with auxiliary fuel (A heavy oil) to generate power.The amount of biomass that can be processed per day is 4 to 8. The rated output of the generator is 100 kilowatts, of which 50 kilowatts is self-consumed by the plant and 50 kilowatts is transmitted to SA, which uses the generated electricity for lighting in the toilets and parking lots. In addition to being used as fuel for power generation, the generated gas is also circulated as energy for heating biomass.Carbonized materials other than gas are reduced to 1/10 of the weight of plant-generated materials.Exhaust heat from generators is also used to dry biomass, which is used as an energy source. We are improving efficiency.Because the biomass is steamed and gasified from the outside, harmful substances such as dioxins are not generated."

In the system described in Non-Patent Document 1, there is no suggestion about the temperature at which the circulating cleaning water is sprayed. In the system described in Non-Patent Document 1, the tar could not be removed, the tar interfered with the plant operation, and the plant could not be operated continuously for more than several days.

JP 2018-105610 JP 2014-125577

Nikkan Kensetsu Kogyo Shimbun "East Japan Expressway Company / Consideration of development and expansion of biomass power generation facilities / Practical use at Tohoku Expressway Nasu Kogen Service Area August 8, 2016 Page 4" <URL: https://www.decn.co.jp/? p=74521 > March 10, 2020

To provide an apparatus for heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace, and capable of continuous operation without causing trouble due to generation of clinker.

To provide a device for heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace to generate power, which is capable of continuous operation without causing trouble to the plant due to tar.

An object of the present invention is to provide an apparatus capable of collectively using plant biomass of various plant types, parts, and sizes as a gasification target without worrying about moisture content or the like.

(1) Thermal decomposition means for heating plant biomass at 800° C. or less and discharging thermal decomposition gas, and tar component removal means for removing tar components from the thermal decomposition gas at 650° C. to 780° C. discharged from the thermal decomposition means. and a biomass gasifier that solves the problem.
(2) The problem is solved by the biomass gasifier according to (1), characterized in that the plant biomass is heated in a rotary kiln type furnace.
(3) The problem is solved by the biomass gasifier according to (2), wherein the plant biomass is a herbaceous plant or bamboo.
(4) In the thermal decomposition means, the thermal decomposition gas discharged from the thermal decomposition means is used as energy for heating, and the temperature control in the thermal decomposition means is controlled by the temperature inside the thermal decomposition means and the temperature inside the thermal decomposition means. The problem is solved by the biomass gasifier according to any one of (1) to (3), characterized in that the heating is performed from the viewpoint of the temperature at which the pyrolysis means is heated.
(5) The biomass gasifier according to any one of (1) to (4), wherein the tar component removing means includes a water scrubber that blows water onto the pyrolysis gas to remove the tar component. to solve the problem.
(6) The biomass gasifier according to any one of (1) to (5), wherein the tar component removing means includes an oil scrubber that blows oil onto the pyrolysis gas to remove the tar component. to solve the problem.
(7) The problem is solved by the biomass gasifier according to any one of (1) to (6), characterized by comprising a char collecting means for separating and collecting char generated by heating the plant biomass.
(8) The problem is solved by the biomass gasifier according to any one of (1) to (7), which is characterized by comprising power generation means for generating power using the pyrolysis gas.

It is desirable to suppress generation of clinker by gasifying silica or the like without burning. Therefore, by setting the heating temperature of the plant biomass to 800° C. or lower, the silica is gasified without being used as fuel. Therefore, the heating temperature of plant biomass is set to 800° C. or lower.
Heating is performed using a rotary kiln type furnace. By using a rotary kiln type furnace, the problem of sand and char segregation as seen in fluidized bed type furnaces is eliminated. In gasification, unlike combustion, the temperature inside the furnace can be almost the same as the temperature for heating biomass, so the temperature for heating biomass can be easily controlled.

Remove tar from the gas freshly discharged from the cracking furnace. Since the temperature inside the pyrolysis furnace is set at 650°C to 780°C, the temperature at which the tar component is removed from the pyrolysis gas is 650°C to 780°C. When the temperature of the pyrolysis gas is between 650° C. and 780° C., the tar component is in a vaporized state before becoming actualized in a liquid or solid state. The tar component can be removed satisfactorily by removing it in a vaporized state. The reason why the temperature in the kiln is set to 650° C. or higher is that if the temperature in the kiln is 650° C. or lower, the gasification speed of biomass becomes extremely slow and the quality of the gasified gas deteriorates.

To provide an apparatus for heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace to generate power, and capable of continuous operation without causing trouble due to the generation of clinker.

It is possible to obtain a device for heating herbaceous plants and bamboo in a pyrolysis furnace to gasify them to generate power, which can be operated continuously without being disturbed by tar.

It is possible to obtain an apparatus that can collectively use plant biomass of various plant types, parts, and sizes as a gasification target without worrying about moisture content or the like.

2 shows the flow of the plant in Example 1. FIG. The energy flow is added to the flow of Example 1. FIG. The flow rate of pyrolysis gas and the like are shown by comparing the plant of Example 1 and the old plant. The power generation amount and the like are shown by comparing the plant of Example 1 and the old plant. The flow of conventional biomass gas power generation is shown.

1. Configuration of Power Generation System The configuration of the plant in Example 1 will be described with reference to FIG. Raw materials are stored in the raw material storage yard 10 . The raw material is conveyed to the silo 20 via a belt conveyor and dried to some extent in the silo.

The raw material is subsequently conveyed to the weighing device 30 via the belt conveyor, and charged into the rotary kiln 40 after being weighed. The rotary kiln 40 is externally heated with the gas obtained from the heating gas generating furnace 100 . The raw material is heated in a rotary kiln 40 in a substantially oxygen-free state while being rotated by the rotation of the kiln to generate pyrolysis gas.

The temperature in the rotary kiln is controlled to maintain 720°C-760°C. Details of the control will be described later. The gas generated in the rotary kiln 40 flows into the dust collector 50 while maintaining a temperature (approximately 720° C. to 760° C.) that is almost the same as after generation. As the dust collector 50, two types are used: a chamber type dust collector (not shown) and a cyclone type dust collector (not shown). In chamber dust collectors, relatively large char falls by gravity onto a conveyor (not shown) below. The generated gas continues to flow into a cyclonic precipitator at a substantially constant temperature, where the relatively fine char is collected by centrifugal force and falls to a conveyor (not shown) below. The char that falls from the chamber dust collector and the cyclone dust collector toward the conveyor is transported and stored by the conveyor.

The generated gas continues to flow into the water scrubber 60 while maintaining approximately the temperature at which it was generated, and is sprayed with a spray of water. As a result, the hydrophilic tar component mixed in the gas in a vaporized state is removed. When the temperature of the gas cools down, the tar becomes liquid or solid. By removing the tar in the vaporized state, the generation of tar when the gas cools down can be significantly reduced. The water scrubber 60 has a mechanism for suppressing the temperature rise of the sprayed water, thereby rapidly lowering the temperature of the generated gas and promoting the liquefaction and solidification of the tar to remove it. The generated gas 45 that has passed through the water scrubber 60 continues to flow into the oil scrubber 70 and is sprayed with oil in the form of a spray. This removes the lipophilic tar component in the gas. Referring to FIG. 1, the evolved gas then flows into a submicron filter 80 to remove submicron-sized tar components remaining in the gas. In the process up to this point, almost all tar components in the gas are removed. Subsequently, the gas is fed into the cylinders of the generator 90 by the blower, and the engine is driven to generate electricity.

With reference to FIG. 2, the energy flow will be added to the flow of the first embodiment. The gas from the heating gas generating furnace 100 is used for heating the kiln 40 (arrow a in FIG. 2). The gas from which almost all tar components have been removed through the submicron filter 80 is used as fuel in the heating gas generating furnace (arrow b). In addition, the plant is provided with auxiliary fuel 130 such as A heavy oil, and when the supply of biomass-derived energy (arrow b) is insufficient, it is used as a fuel for the heating gas generation furnace 100 that obtains the heat source of the rotary kiln ( arrow c).

The oil used to remove the lipophilic tar in the gas with the oil scrubber 70 is then used as fuel for the heating gas generator 100 that obtains the heat source of the rotary kiln while still containing the tar (arrow d). The auxiliary fuel 130 is also used as energy for power generation by the generator 90 when the supply of biomass-derived energy is insufficient (arrow e). Electricity obtained by power generation is used for system operation such as heating of hot air sent into the silo 20 (arrow f). Although not shown, the electricity obtained by power generation is also sold if it is surplus as described above.

2. Pyrolysis Gas Flow Rate and Power Generation Amount FIG. 3 shows a comparison of the pyrolysis gas flow rates and the like between the plant of Example 1 and the old plant. The values shown in the table of FIG. 3 are average values per hour on a certain day. The old plant is the plant shown in Non-Patent Document 1. That is, the old plant does not have a means for removing tar components at high temperatures and an oil scrubber for removing lipophilic tar components. At the old plant, tar becomes apparent due to the operation of the plant, hindering the plant, and the plant cannot continue to operate.

As shown in FIG. 2, the pyrolysis gas from which tar has been removed (referred to as “dry gas” in the table of FIG. 3) is used as energy in two places, the generator 90 and the heating gas generator 100 (arrow b). used. Therefore, by measuring the "flow rate of dry gas supplied to the heating gas generator" and the "flow rate of dry gas supplied to the generator", the total amount of pyrolysis gas discharged from each plant can be known to some extent.

A comparison of the "flow rate of dry gas supplied to the heating gas generator" and the "flow rate of dry gas supplied to the generator" in FIG. 3 between the plant of Example 1 and the old plant is as follows. In the plant of Example 1, adding the "flow rate of dry gas supplied to the heating gas generator" and the "flow rate of dry gas supplied to the generator" gives 19.8 + 32.7 = 52.5 (Nm ³ /h). be. On the other hand, in the old plant, adding the "flow rate of dry gas supplied to the heating gas generator" and the "flow rate of dry gas supplied to the generator" gives 0+20.0=20.0 (Nm ³ /h).

FIG. 4 shows the "dry gas flow rate to generator", "A heavy oil supply amount to generator" and "power generation" in the plant of Example 1 and the old plant. The values shown in the table of FIG. 4 are average values per hour on the same date and time as those shown in FIG.

The "dry gas flow rate to the generator" averages 32.7 Nm3/h for the Example 1 plant, while it averages 20.0 Nm3/h for the old plant. The "A heavy oil supply amount to the generator" is 5.2 L/h on average in the plant of Example 1, while it is 21.3 L/h on average in the old plant. The "power generation amount" is 71.6 KW on average for the plant of Example 1, while it is 91.4 KW on average for the old plant.

Using the values in FIG. 4, the ratio of the amount of heat used for power generation by the supplied dry gas to the auxiliary fuel A heavy oil for each of the plant of Example 1 and the old plant is calculated as follows. is.

here,
Amount of heat given to gas = flow rate (Nm3/h) x calorific value per unit of dry gas (MJ/Nm3)
Calorific value per unit of dry gas = 14.7 (MJ/Nm3)
Also here,
Heat value obtained by oil = flow rate (L/h) x specific gravity (kg/L) x calorific value per unit of dry gas (MJ/kg)
Specific gravity = 0.85 (kg/L)
Calorific value per unit of dry gas = 38.9 (MJ/kg)

[Plant of Experimental Example 1]
Dry gas 32.7×14.7=480.7 (MJ/h)
Heavy oil 5.2 x 0.85 x 38.9 = 171.9 (MJ/h)
Dry gas: heavy oil = 480.7: 171.9 = 1: 0.36
[Old plant]
Dry gas 20.0 x 14.7 = 294.0 (MJ/h)
Heavy oil 21.3 x 0.85 x 38.9 = 704.3 (MJ/h)
Dry gas: Heavy oil = 294.0: 704.3 = 1: 2.40

That is, in the plant of Example 1, the amount of heat used to obtain the set amount of power was 1 from the dry gas and 0.36 from the auxiliary fuel. Also, in the old plant, the amount of heat used to obtain the set amount of power was 1 from the dry gas and 2.40 from the auxiliary fuel. From this, it can be seen that the plant of Example 1 uses a very small amount of auxiliary fuel as compared with the old plant.

3. Clinker generation and kiln temperature control The temperature in the kiln and the temperature of the gas that heats the kiln (i.e., the temperature of the heated gas generated from the heated gas generator) so that the temperature in the kiln is maintained between 720°C and 760°C. , are measured, and the following control is performed according to changes in these two temperatures.

(1) Vary the amount of raw material supplied according to the temperature inside the kiln. That is, when the temperature inside the kiln is lower than 720° C., the amount of feedstock is reduced. When the temperature inside the kiln is higher than 760°C, the amount of feedstock is increased.
(2) If the amount of raw material supplied is reduced, the amount of gas generated will decrease, and the amount of gas supplied to the heating gas generating furnace will also decrease. Supplementary fuel is used when the temperature of the gas that heats the kiln is not raised sufficiently by increasing the cooking rate.
(3) If the temperature inside the kiln cannot be prevented from dropping even with the use of auxiliary fuel, for example, if it falls below 650° C., the supply of raw materials is stopped and the temperature inside the kiln is waited for to rise. As soon as it is confirmed that the temperature inside the kiln has risen to 650°C, the raw material is re-supplied step by step.
(4) When the temperature inside the kiln exceeds 760° C., the temperature of the gas that heats the kiln is lowered or the amount of biomass raw material supplied is lowered so that the proper temperature can be maintained.

As described above, by controlling the temperature inside the kiln from two viewpoints, the temperature inside the kiln and the temperature of the gas that heats the kiln, it is not necessary to measure the moisture content of the input biomass. In a conventional biomass gasifier, the moisture content of biomass is measured and the amount of biomass to be fed into the kiln is determined according to the moisture content of the biomass. Instead, the temperature inside the kiln can be controlled by measuring only two temperatures. Since biomass has a wide range of moisture contents, the fact that biomass can be used as a raw material for gasification regardless of its moisture content is of great significance in terms of work efficiency and cost reduction.

10 raw material storage yard 20 silo 30 scale 40 rotary kiln 45 generated gas 50 dust collector 60 water scrubber 61 water seal conveyor 62 water seal tank 63 sludge 64 wash water circulation pump 65 auto strainer 66 wash water cooler 67 cooling water 68 injection hole 70 oil scrubber 80 Submicron filter 90 Generator 100 Heating gas generator 110 Waste oil tank 120 Kitchen 130 Auxiliary fuel 140 SA (service area)

Claims (8)

pyrolysis means for heating plant biomass at 800° C. or less and discharging pyrolysis gas;
and a tar component removing means for removing tar components from the pyrolysis gas at 650° C. to 780° C. discharged from the pyrolysis means. 2. The biomass gasifier according to claim 1, wherein the plant biomass is heated in a rotary kiln type furnace. 3. The biomass gasifier according to claim 2, wherein the plant biomass is a herbaceous plant or bamboo. In the pyrolysis means, the pyrolysis gas discharged from the pyrolysis means is used as energy for heating,
4. The biomass gas according to any one of claims 1 to 3, wherein the temperature control in the thermal decomposition means is performed from the viewpoint of the internal temperature of the thermal decomposition means and the temperature at which the thermal decomposition means is heated. conversion device. 5. The biomass gasifier according to any one of claims 1 to 4, wherein the tar component removing means comprises a water scrubber that blows water onto the pyrolysis gas to remove the tar component. 6. The biomass gasifier according to any one of claims 1 to 5, wherein the tar component removing means comprises an oil scrubber that blows oil onto the pyrolysis gas to remove the tar component. 7. The biomass gasifier according to any one of claims 1 to 6, further comprising char collecting means for separating and collecting char produced by heating the plant biomass. 8. The biomass gasifier according to any one of claims 1 to 7, further comprising power generation means for generating power using the pyrolysis gas.

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