Biomass gasification device

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

[Technical Field]

[0001] This relates to a plant biomass gasification device that operates at a predetermined heating temperature. [Background technology]

[0002] When developing forests, large parks, highway slopes, and other areas, mowing and pruning produce large amounts of branches and leaves. Using these as an energy resource without waste disposal would be desirable, both in terms of reducing waste disposal costs and in terms of the future outlook for global energy. However, when herbaceous plants are burned, the potassium oxide and silica in the ash react to produce large amounts of clinker, making them unsuitable for combustion. Furthermore, while fluidized-bed furnaces are commonly used for gasification, the need for char disposal makes gasification using a fluidized-bed furnace problematic. For this reason, branches and leaves resulting from mowing and pruning are generally disposed of as waste. Bamboo, like herbaceous plants, also suffers from the same problems as herbaceous plants due to its high silicon and potassium content, making its use as an energy resource difficult. This has led to an increase in abandoned bamboo forests. Given these circumstances, there has been a worldwide demand for the development of systems that effectively utilize herbaceous plants and bamboo as energy resources.

[0003] Furthermore, in equipment that gasifies plants, including herbs and bamboo, into biomass, the tar generated during the gasification process has hindered continuous operation.

[0004] Furthermore, plant biomass generated by mowing, sorting, etc. contains a variety of plants and various plant parts, such as leaves, stems, and roots. Therefore, the plant biomass generated by mowing, sorting, etc. is a miscellaneous mixture of plants with various moisture contents. When using plant biomass as a feedstock for a gasification system, measuring the moisture content of the plant biomass and aligning it to a constant value is one way to suppress the generation of tar and clinker, but the additional steps required to do so have created problems in terms of cost and time.

[0005] Patent Document 1 describes a combustion device that uses bamboo as a biomass fuel. In this invention, in order to solve the problem of clinker generation when using bamboo as fuel, the bark of trees such as cedar and cypress is mixed with the bamboo and burned, and the calcium oxide in the ash from the bark prevents the generation of clinker. The device described in this document does not suggest the idea of ​​preventing clinker generation by temperature control.

[0006] Patent Document 2 describes a biomass gas generator that reduces the generation of tar by including a process of injecting water into the generated gas. However, in the device described in this document, the temperature of the generated gas is about 300°C, which does not vaporize the tar, and there is no suggestion of condensing and recovering the vaporized tar at a high temperature range of 650°C to 780°C.

[0007] Non-Patent Document 1 describes a system (Figure 5) in which biomass is chipped and heated in a pyrolysis furnace to gasify it as follows: The following is written about a system called "a new green recycling system using biomass gas power generation." "The biomass gas power generation system works by drying chipped biomass in a dryer, then heating and roasting it in a pyrolysis furnace to break it down into pyrolysis gas and charcoal. The tar and fine soot contained in the pyrolysis gas are purified by spraying circulating clean water on it. The final purified pyrolysis gas is sent to a generator, where it is mixed with auxiliary fuel (heavy oil A) to generate electricity. The generator has a rated output of 100 kilowatts, with 50 kilowatts for self-consumption within the plant and 50 kilowatts for transmission to the SA. The generated electricity is used for toilets, parking lot lighting, and other purposes in the SA. In addition to being used as fuel for power generation, the gas generated in the process is also circulated as heating energy for biomass. The weight of charcoal other than gas is reduced to one-tenth of the weight of plant-derived material. The exhaust heat from the generator is also used to dry the biomass, improving energy efficiency. Because the biomass is gasified by roasting it externally, no harmful substances such as dioxins are produced."

[0008] The system described in Non-Patent Document 1 does not suggest any temperature at which the circulating cleaning water is sprayed. The system described in Non-Patent Document 1 was unable to remove tar, which interfered with plant operation, making it impossible to operate the plant continuously for more than a few days. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent Publication No. 2018-105610 [Patent Document 2] Patent Publication No. 2014-125577 [Non-patent literature]

[0010] [Non-Patent Document 1] Nikkan Kensetsu Kogyo Shimbun, "East Nippon Expressway Company / Considerations for expansion of biomass power generation facilities / Practical application at Nasu Kogen SA on the Tohoku Expressway, August 8, 2016, Page 4"<URL:https: / / www.decn.co.jp / ?p=74521> March 10, 2020 Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to provide an apparatus for heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace, which can be operated continuously without any trouble caused by the generation of clinker.

[0012] To provide an apparatus for generating electricity by heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace, which can be operated continuously without causing any trouble to the plant due to tar.

[0013] The present invention aims to provide an apparatus that can collectively gasify plant biomass of various types, parts, and sizes of plants without regard to moisture content, etc. [Means for solving the problem]

[0014] (1) The problem is solved by a biomass gasification system equipped with a pyrolysis means for heating plant biomass at 800°C or less and discharging pyrolysis gas, and a tar component removal means for removing tar components from the pyrolysis gas at 650°C to 780°C discharged from the pyrolysis means. (2) The problem is solved by the biomass gasification apparatus described in (1), which is characterized in that plant biomass is heated in a rotary kiln-type furnace. (3) The problem is solved by the biomass gasification apparatus according to (2), characterized in that the plant biomass is a herbaceous plant or bamboo. (4) The problem is solved by a biomass gasification apparatus according to any one of (1) to (3), characterized in that in the pyrolysis means, the pyrolysis gas discharged from the pyrolysis means is used as energy for heating, and the temperature in the pyrolysis means is controlled in terms of the temperature inside the pyrolysis means and the temperature at which the pyrolysis means is heated. (5) The problem is solved by a biomass gasification apparatus according to any one of (1) to (4), characterized in that the tar component removal means is equipped with a water scrubber that sprays water onto the pyrolysis gas to remove tar components. (6) The problem is solved by a biomass gasification apparatus according to any one of (1) to (5), characterized in that the tar component removal means is equipped with an oil scrubber that sprays oil onto the pyrolysis gas to remove tar components. (7) The problem is solved by a biomass gasification apparatus according to any one of (1) to (6), which is characterized by including a char collection means for separating and collecting char generated by heating plant biomass. (8) The problem is solved by a biomass gasification apparatus according to any one of (1) to (7), which is characterized by including a power generation means for generating electricity using the pyrolysis gas.

[0015] It is desirable to suppress the generation of clinker by gasifying silica and other materials without burning them. Therefore, by setting the heating temperature of plant biomass at 800°C or less, silica will be gasified without using it as fuel. For this reason, the heating temperature of plant biomass is set at 800°C or less. Heating is carried out using a rotary kiln-type furnace. By using a rotary kiln-type furnace, the problem of separation of sand and char, which is seen in fluidized bed furnaces, is eliminated. Also, in gasification, unlike combustion, the temperature inside the furnace is almost the same as the temperature at which the biomass is heated, making it easier to control the temperature at which the biomass is heated.

[0016] Tar is removed from the gas shortly after it is discharged from the pyrolysis furnace. Because the temperature inside the pyrolysis furnace is set to 650°C to 780°C, the temperature for removing tar components from the pyrolysis gas is 650°C to 780°C. When the temperature of the pyrolysis gas is 650°C to 780°C, the tar components are in a vaporized state before they become liquid or solid. By removing the tar components in this vaporized state, they can be effectively removed. The temperature inside the kiln is set to 650°C or higher because, if the temperature inside the kiln falls below 650°C, the speed of biomass gasification becomes extremely slow and the quality of the gasified gas deteriorates. [Effects of the Invention]

[0017] The present invention provides an apparatus that generates electricity by heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace, and that can operate continuously without any problems caused by the generation of clinker.

[0018] The device generates electricity by heating and gasifying herbaceous plants and bamboo in a pyrolysis furnace, and can operate continuously without any problems caused by tar.

[0019] It is possible to obtain an apparatus that can collectively gasify plant biomass of various types, parts, and sizes of plants without having to worry about moisture content, etc. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows the flow of the plant in Example 1. [Figure 2] The flow of energy is added to the flow of Example 1. [Figure 3] The flow rate of pyrolysis gas and the like are shown in comparison between the plant of Example 1 and the old plant. [Figure 4] The amount of power generated and other data are shown by comparing the plant of Example 1 with the old plant. [Figure 5] This shows the flow of conventional biomass gas power generation. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0021] 1. Power generation system configuration The configuration of the plant in Example 1 will be described with reference to Figure 1. Raw materials are stored in a raw material storage yard 10. The raw materials are transported to a silo 20 via a belt conveyor, and are dried to some extent in the silo.

[0022] The raw materials are then transported via a belt conveyor to a weighing scale 30, where they are weighed and then fed into a rotary kiln 40. The rotary kiln 40 is heated from the outside by gas obtained in a heated gas generator 100. Inside the rotary kiln 40, the raw materials are heated in a substantially oxygen-free environment while rotating due to the rotation of the kiln, and pyrolysis gas is generated.

[0023] The temperature inside the rotary kiln is controlled to be maintained between 720°C and 760°C. Details of this control will be described later. The gas generated inside 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 when it was generated. Two types of dust collectors are used: a chamber-type dust collector (not shown) and a cyclone-type dust collector (not shown). In a chamber-type dust collector, relatively large char falls by gravity toward a conveyor (not shown) below. The generated gas then flows into the cyclone-type dust collector while maintaining its temperature, and relatively fine char is collected by centrifugal force and falls toward the conveyor (not shown) below. The char that falls from the chamber-type dust collector and cyclone-type dust collector toward the conveyor is transported by the conveyor and stored.

[0024] The generated gas then flows into the water scrubber 60, maintaining its temperature at approximately the same level as when it was generated, where it is sprayed with a water spray. This removes hydrophilic tar components that are vaporized and mixed into the gas. Tar becomes apparent in liquid or solid form as the gas cools. By removing the tar in its vaporized state, the generation of tar when the gas cools can be significantly reduced. The water scrubber 60 is equipped with a mechanism to suppress the temperature rise of the sprayed water, thereby rapidly lowering the temperature of the generated gas and promoting the liquefaction and solidification of tar for removal. After passing through the water scrubber 60, the generated gas 45 then flows into the oil scrubber 70, where it is sprayed with oil. This removes lipophilic tar components from the gas. Referring to Figure 1, the generated gas then flows into the submicron filter 80, where the remaining submicron-sized tar components are removed by the filter. Almost all of the tar components in the gas are removed by this process. The gas is then forced by a blower into the cylinder of a generator 90, which drives the engine and generates electricity.

[0025] With reference to Figure 2, the flow of Example 1 will be explained with the addition of energy flow. Gas from the heated gas generator 100 is used to heat the kiln 40 (arrow a in Figure 2). The gas, from which almost all tar components have been removed after passing through the submicron filter 80, is used as fuel in the heated gas generator (arrow b). The plant is also provided with auxiliary fuel 130, such as heavy oil A, which is used as fuel for the heated gas generator 100 to obtain the heat source for the rotary kiln when the supply of biomass-derived energy (arrow b) is insufficient (arrow c).

[0026] The oil used to remove lipophilic tar from the gas in the oil scrubber 70 is then used, still containing the tar, as fuel for the heated gas generator 100, which provides the heat source for the rotary kiln (arrow d). The auxiliary fuel 130 is also used as energy for generating electricity for the generator 90 when the supply of biomass-derived energy is insufficient (arrow e). The electricity obtained by the power generation is used to operate the system, for example, to heat the hot air sent into the silo 20 (arrow f). Although not shown, any surplus electricity obtained by the power generation can also be sold.

[0027] 2. Pyrolysis gas flow rate and power generation amount Figure 3 shows a comparison of the flow rate of pyrolysis gas between the plant of Example 1 and the old plant. The values ​​shown in the table in Figure 3 are average values ​​per hour on a certain day. The old plant is the plant shown in Non-Patent Document 1. In other words, the old plant is not equipped with a means for removing tar components at high temperatures or an oil scrubber for removing lipophilic tar components. In the old plant, tar becomes apparent during plant operation, causing problems and preventing the plant from continuing to operate.

[0028] As shown in Figure 2, the pyrolysis gas from which tar has been removed (referred to as "dry gas" in the table in Figure 3) is used as energy in two places: the generator 90 and the heated gas generator 100 (arrow b). Therefore, by measuring the "flow rate of dry gas supplied to the heated gas generator" and the "flow rate of dry gas supplied to the generator," the total amount of pyrolysis gas emitted from each plant can be determined to some extent.

[0029] In Figure 3, the "flow rate of dry gas supplied to the heating gas generator" and the "flow rate of dry gas supplied to the generator" are compared between the plant of Example 1 and the old plant, as follows: In the plant of Example 1, the "flow rate of dry gas supplied to the heating gas generator" and the "flow rate of dry gas supplied to the generator" are added together to get 19.8 + 32.7 = 52.5 (Nm 3 / h). 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).

[0030] Figure 4 shows the "flow rate of dry gas to the generator," "amount of heavy oil A supplied to the generator," and "power generation amount" for the plant in Example 1 and the old plant. The values ​​shown in the table in Figure 4 are average values ​​per hour for the same date and time as those shown in Figure 3.

[0031] The "flow rate of dry gas to the generator" is 32.7 Nm3 / h on average in the plant of Example 1, while it is 20.0 Nm3 / h on average in the old plant. The "amount of heavy oil A supplied 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 in the plant of Example 1, while it is 91.4 kW on average in the old plant.

[0032] Using the values ​​in Figure 4, the ratio of the amount of heat used in power generation from the supplied dry gas to that from the auxiliary fuel A heavy oil was calculated for each of the plant in Example 1 and the old plant, and the results are as follows.

[0033] where: 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, Amount of heat 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)

[0034] [Plant for Experimental Example 1] Dry gas 32.7 x 14.7 = 480.7 (MJ / h) Heavy oil 5.2×0.85×38.9=171.9(MJ / h) Dry gas:heavy oil = 480.7:171.9 = 1:0.36 [Old plant] Dry gas 20.0×14.7=294.0(MJ / h) Heavy oil 21.3×0.85×38.9=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 generate a set amount of electricity from dry gas was 1, while that from auxiliary fuel was 0.36. Also, in the old plant, the amount of heat used to generate a set amount of electricity from dry gas was 1, while that from auxiliary fuel was 2.40. This shows that the plant of Example 1 uses much less auxiliary fuel than the old plant.

[0035] 3. Clinker generation and kiln temperature control To maintain the temperature inside the kiln at 720°C to 760°C, two temperatures are measured: the temperature inside 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), and the temperature is controlled as follows according to changes in these two temperatures.

[0036] (1) The amount of raw material supplied is changed according to the temperature inside the kiln. That is, if the temperature inside the kiln is lower than 720°C, the amount of raw material supplied is reduced. If the temperature inside the kiln is higher than 760°C, the amount of raw material supplied 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 generator will also decrease, so the amount of fuel added will increase to raise the temperature of the gas that heats the kiln. If the temperature of the gas that heats the kiln does not rise sufficiently even after increasing the amount of fuel added, auxiliary fuel will be used. (3) If the temperature inside the kiln cannot be prevented from dropping even with the use of auxiliary fuel, for example, if it drops below 650°C, stop the supply of raw materials and wait for the temperature inside the kiln to rise. Once it is confirmed that the temperature inside the kiln has risen to 650°C, gradually resupply raw materials. (4) If the temperature inside the kiln exceeds 760°C, the temperature of the gas heating the kiln or the amount of biomass raw material supplied will be reduced to maintain an appropriate temperature.

[0037] As described above, by controlling the temperature inside the kiln from two perspectives, that is, the temperature inside the kiln and the temperature of the gas heating the kiln, there is no need to measure the moisture content of the biomass being fed. In conventional biomass gasification systems, the moisture content of the biomass is measured and the amount of biomass to be fed into the kiln is determined based on the moisture content of the biomass. However, with the above-described method, the temperature inside the kiln can be controlled by measuring only two temperatures, regardless of the moisture content of the biomass. Since biomass has a wide range of moisture contents, being able to use biomass as a gasification feedstock regardless of its moisture content is of great significance in terms of improving work efficiency and reducing costs. [Explanation of symbols]

[0038] 10 Raw material storage yard 20 Silo 30 Measuring instrument 40 Rotary Kiln 45 Evolved gas 50 Dust collector 60 Water Scrubber 61 Water-sealed conveyor 62 Water seal tank 63 Sludge 64 Cleaning water circulation pump 65 Auto Strainer 66 Washing 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

1. a pyrolysis means for heating the plant biomass at 800°C or less and discharging pyrolysis gas; a tar component removal means for removing tar components from the pyrolysis gas at 650°C to 780°C discharged from the pyrolysis means.

2. 2. The biomass gasification apparatus according to claim 1, wherein the plant biomass is heated in a rotary kiln-type furnace.

3. 3. The biomass gasification apparatus according to claim 2, wherein the plant biomass is a herbaceous plant or bamboo.

4. In the pyrolysis means, the pyrolysis gas discharged from the pyrolysis means is used as energy for heating, 4. The biomass gasification apparatus according to claim 1, wherein the temperature in the pyrolysis means is controlled in terms of the temperature inside the pyrolysis means and the temperature to which the pyrolysis means is heated.

5. 5. The biomass gasification apparatus according to claim 1, wherein the tar component removing means comprises a water scrubber that sprays water onto the pyrolysis gas to remove tar components.

6. 6. The biomass gasification apparatus according to claim 1, wherein the tar component removal means comprises an oil scrubber that sprays oil onto the pyrolysis gas to remove tar components.

7. 7. The biomass gasification apparatus according to claim 1, further comprising a char collection means for separating and collecting char produced by heating the plant biomass.

8. The biomass gasification apparatus according to any one of claims 1 to 7, further comprising a power generation means for generating electricity using the pyrolysis gas.

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