JP2015221868A - Material accumulation type production facility for biomass pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of biomass pellets which uses thinned wood and waste wood as raw materials, avoids the risk of self-ignition combustion while increasing the moisture drying limit, achieves water resistance and improves the production efficiency by reducing energy and time necessary for production.SOLUTION: A production method of biomass pellets comprises charging crushed wood into an oven which has vertically a heating reduction drier for drying wood and a cooling tower for heat recovery of biomass pellets and guides waste heat-recovered heating air sucked from a connection part between the heating reduction drier and the cooling tower to the oven for combustion of raw material chips and product refuse to generate a heating reduction dry gas and blow to the heating reduction drier, drawing out dried wood from the lower part of the heating reduction drier, pelletizing by a compression pressurization machine, transferring to the cooling tower to recover waste heat for energy saving.

Description

   The present invention relates to a material-integrated biomass pellet manufacturing facility using thinned wood or waste wood.

In the old days, in order to make up for the shortage of household coal fuel during post-war reconstruction, the form of a lotus root-like firewood that is called “Ogarite” that regenerates wood sawdust generated during sawing and uses it as fuel. Then, biomass fuel called ogarite was made on the principle of solidification by carbonization of wood fats and oils by drying and compressing sawdust so that it can be distributed. However, at that time, it was an alternative to wood and coal, so it did not require an automated form of fuel for combustion.
The purpose of the present biomass fuel is a substitute fuel for coal and oil, which are fossil fuels, and is required to be applied to combustion facilities such as power plants. That is, it requires short-time combustion similar to heavy oil (a fuel form with easy combustion control), low ash content, and capable of co-firing, and the technology proven in the past cannot be applied.

   On the other hand, biomass fuel made from wood carbonization has a long history of charcoal. In order to make charcoal, high-purity individual carbonization can be achieved by commonly known “charcoal baking” of wood in a reduction furnace. Furthermore, the charcoal produced can be easily crushed, so that it meets the technical requirements. However, natural wood contains a large amount of hydrogen in addition to carbon. Ideally, it would be ideal to simply remove the water, solidify by carbonization, and be easily pulverized before combustion, but as a result, the production of charcoal requires a large amount of energy, leaving only carbon, making it practical. Because it is scarce, it does not apply to biomass pellet production.

For this reason, as a method for maximizing combustion energy efficiency, the wood is dried and heated to about 140 ° C. with a rotary kiln, etc., and then the content of fats and oils is reduced by compression of about 1 MPa by a rotary pressure roller punching method. Biomass pellets using the initial carbonization principle were born. This is the mainstream method for producing biomass pellets, but it has major drawbacks.
Biomass pellets in solidification by initial carbonization are dried, but have a better function of absorbing environmental moisture than natural wood. That is, it cannot be stored or moved on the street. Furthermore, it absorbs moisture in the air. Moisture absorption causes bacteria to grow and induces the generation of malodours, causing logistics and management problems.

In order to solve this problem, what was recently invented in Japan is called “biomass coke”. This is because the wood chips are solidified at a temperature of 180-200 ° C under conditions of about 200-220 ° C high-temperature dry air (high-temperature oxidation drying furnace) with a rotary kiln, etc., and a piston double-acting pressure holding condition of about 10 MPa. Is a bit-like biomass coke with a combustion performance close to that of coke, with a surface area of about 2 kg and carbonization by raising the heating carbonization temperature to the limit where it does not self-ignite wood. This technology was developed for the purpose of obtaining regenerated fuel using thinned wood, so that it overcomes the disadvantages of water pellets that are weak in water resistance, which was a problem in the past, and makes biomass coke from raw materials obtained by grinding thinned wood. In addition, there is a feature that enables production with less energy.
However, it can be used in coke ovens as a biomass fuel by solving the purpose of regeneration of thinned wood and water resistance, but it is difficult to grind necessary for heavy oil co-firing in application conditions. In order to improve water resistance, it requires a solid body with a high density and a small surface area, which makes pulverization difficult.

Biomass pellets, commonly called “black pellets”, invented in the forest kingdom and the eco-friendly countries of the United States and the EU, are manufactured using the same technique as biomass coke, but for the purpose of producing pellets, The pressurized container is as small as 6 to 8 mm. However, high temperature hot air is required to reach the target temperature in a short time because it is necessary to dry the wood using a rotary kiln with the same heating conditions at the limit temperature of self-ignition and to heat it at 180 to 200 ° C. Furthermore, pressure solidification is the same, requiring a lot of production time and energy consumption. As a result, carbonization progresses to the point where the color of the product is darkened (dark brown), and the water resistance is such that it can be stored outdoors for a few weeks even in the rainy season (swelling is less if it is about 1 week in water). It ’s all over. The pellets that have been blackened by this carbonization, ie, “black pellets”, have solved the water resistance problem.
However, this invention requires further solutions to the problems. Since heat drying using an oxidation furnace is adopted, the moisture drying limit cannot be made high. Therefore, it is necessary to dry over a period of time until carbonization immediately before self-combustion, and much drying energy is required. Furthermore, it takes a long time to extract and solidify the fat and oil contained in the wood. That is, low production efficiency and further improvement in water resistance are required. Although black pellets are not a problem in a coal furnace, a heavy oil mixed-fired furnace that requires fine pulverization also needs to be solved because pulverization is difficult as in biomass coke.

   On the other hand, cultivation of wood, which is a raw material for biomass pellets, is the fastest growing species of willow seeds in dry areas, pine seeds in temperate cities, and eucalyptus seeds in tropical areas. All species can be harvested every year after planting and cultivated as raw materials. Moreover, the growth cultivation amount is about 1 to 3 kg per square meter per year, which is suitable for land use that is not suitable for food cultivation on the earth. Furthermore, if the price of fossil fuels for oil and coal is high, a large amount of biomass energy can be supplied economically. Here, as the raw material wood for biomass pellets, pine wood is highly cultivated in Japan, willow cultivation in desert areas in China, and eucalyptus cultivation in Southeast Asia. explain. The other materials are basically the same.

Satoshi Takeda, Shunji Shimonaka, Toshiharu Iwatani, Yoshinori Nishino, Shinichi Tamura “Proposal on Reuse of Waste Waste by Biomass” Global Management Society Symposium Global Management 2011 pp. 109-112 2011

Satoshi Takeda, Shunji Shimonaka, Toshiharu Iwatani, Yoshinori Nishino, Shinichi Tamura et al. “Reuse of Waste Materials by Biomass Pelletization” Journal of Global Management Society Vol. 2 March 2014

FIG. 1 shows an example of raw material and final product for processing into a desired pellet with excellent water resistance, taking as an example a crushed piece of pine wood that is predominantly cultivated in temperate regions such as Japan, which constitutes the origin of the present invention. The logical outline of solidification by physical properties and carbonization is shown. Even if it is natural raw wood, thinned wood, and construction waste, the wood is crushed to a maximum particle size of 20 to 50mm and small particle size of 2 to 3mm, although the moisture content is about 10 to 35%, but the constituent materials are the same. The (raw material) contains moisture and fats and oils before processing at room temperature and normal pressure as shown in the model on the left side.
In order to use the raw material as fuel, it is necessary to remove moisture which is a non-combustible material. Water can be removed by heating. On the other hand, in order to use the contained fats and oils as a compression adhesive for dry wood, it is necessary to dissolve the fats and oils, and the higher the temperature, the greater the meltability and the adhesive processing effect. However, since the ignition temperature of the wood is about 230 ° C., the wood starts self-combustion when the moisture is lost and the temperature reaches about 230 ° C. This self-combustion starts from a material that is easier to oxidize than carbon, such as hydrogen, and oxidative combustion occurs. That is, when combustion starts in a chain, carbon also oxidizes and burns. Therefore, the drying conditions and the high-temperature drying temperature were such that the oxidation combustion did not occur, and the heating limit was about 180 to 200 ° C.
The present invention has invented a processing method for increasing this temperature to 200-230 ° C. As a result, biomass pellets having a density of about 1.17 and an apparent volume of 1/8 with a moisture content of 1% or less shown on the right side were obtained. The resulting pellets were found to be water resistant and outperform black pellets and biomass coke. The principle of the invention was that the conventional drying and heating was the drying of an oxidation furnace using a rotary kiln, etc., and because oxidation was promoted (acceleration of combustion ignition) at the time of drying, the limit was 180 to 200 ° C. . Furthermore, carbonization progressed by raising to the limit temperature, leading to blackening.

   FIG. 2 shows the configuration of the present invention. Heat reduction dryer (2) with a structure that allows the heat reduction gas of ~ 230 ° C to pass through the gaps in the pulverized wood that accumulates the raw material sent from the raw wood pulverized raw material manufacturing equipment (1) in the self-supporting vertical fixed moisture removal tower And a vertically fixed cooling tower that recovers about 200 ° C waste heat of the solidified biomass pellets that have the same structure as (1) connected vertically, to dry wood that is heated at the connection The machine to compress and press (3) is installed and connected, the product is taken out from the lower part, and the compression machine is placed in the center of the structure where the raw material is put in from the upper part. Establishing a technology that raises the temperature to a sufficient level and enabling a heat recovery mechanism to succeed in preventing heat loss at high temperatures, and making it possible to produce energy-saving biomass pellets with better thermal efficiency than conventional methods.

   Biomass coke and black pellets of the present invention employ heat drying in an oxidation furnace, so that the drying limit of moisture cannot be taken high, there is a risk of self-ignition combustion at the time of drying, and water resistance is obtained just before ignition. Heating at a high temperature is necessary, and it takes a long time to dry until just before carbonization, which requires a lot of drying energy. Furthermore, since the oil and fat contained in the wood cannot be extracted at a high temperature, it requires a long pressure and time for solidification. That is, the production efficiency is lowered. Further, further improvement in water resistance is required for long-term outdoor storage. Further, although black pellets are applied to a coal furnace, there is a difficulty similar to that of biomass coke in pulverization required for a heavy oil mixed firing furnace that requires fine pulverization and an automated furnace. These solutions are necessary.

   In the heat drying of wood shown in Figs. 1 and 2, combustion gas is made without supplying oxygen sufficiently, the dry wood pieces are stacked about 5-10m high, and about 230 ° C of combustion gas from the bottom is about 0.3 per second. By inserting it at ~ 1m, it will extract self-ignition to about 200-230 ° C, which is completely dry in about 1 minute for small particle wood and 10 minutes for large particle, and extract the joining oil and fat, and about 2 to maximum 20MPa Solidified at low pressure in a short time, energy-saving and mass production of biomass pellets with better water resistance than black pellets became possible.

   The production facility shown in FIG. 3 includes a vertically fixed moisture removing tower tank to a heating / reduction dryer having a structure through which a heating / reducing gas at 230 ° C. is passed and a solidified biomass pellet having a similar structure connected vertically. It has a vertically fixed cooling tower that performs heat recovery at 200 ° C, and heat drying gas drawn from the waste heat recovery heated air sucked from the connecting part is used to burn raw material waste and product waste in a reduction furnace, and the upper part of the drying tower tank By blowing dry wood that has been blown and reduced to a compression and pressurization machine, producing pellets and returning them back to the heat recovery tower, inserting cooling air from the bottom to recover exhaust heat heat, Get energy saving equipment.

   As a result of increasing the extraction of oils and fats in wood by enabling high-temperature treatment for reduction furnace applications that prevented self-ignition, it was found that the water resistance of pellets is several times that of black pellets. Water resistance, energy saving sufficient for practical use, high-speed production, and mass productivity were obtained. In addition, pellets for mixed-firing applications use pellets with a raw material particle size of about 1 mm or less to make pellets that are fragile by adjusting the pellet molding pressure and time. By using a high-speed suction pulverization fan, instantaneous combustion similar to heavy oil combustion can be obtained by collision pulverization of pellets.

FIG. 1 is an explanatory diagram of necessary processing of a biomass pellet raw material (wood piece). (Example 1) FIG. 2 is an explanatory diagram of the basic configuration of the present invention. (Example 2) FIG. 3 is an explanatory diagram of equipment that constitutes the present invention. (Example 3) FIG. 4 is an explanatory view of a vertically arranged heat recovery dryer. (Example 4)

   The material shown in Fig. 3 is delivered to the hopper in a pulverized form, charged into the upper part of the drying tower tank with a closed conveyor, steam discharged from the top of the drying furnace, and cooling air for product exhaust heat recovery from the bottom is injected into the center. Pull out the exhaust heat recovery air at the part, make a high-temperature dry gas of about 230 ° C. reduced and burned such as biomass scrap, return it to the drying tower again, pull out the wood particles that have been sufficiently heated and dried from the center part, Mechanically pressurizing means such as continuous rotation by rotating the screw or compressing and compressing the plunger, solidify into pellets, return to the waste heat recovery tower, and use conventional wood moisture evaporation energy and pressure energy alone. Products over black pellets can be produced with about 1/10 energy. Furthermore, by providing the reduction furnace with an in-house power generation function, it was possible to produce energy and electricity unnecessary for all production.

   In the embodiment of FIG. 1, the raw material of the biomass pellet is mainly a dry wood piece having a moisture content of about 14% from a powdered moisture of about 35% raw wood having a size of 2 to 3 mm. For pellet processing, oil and fat members contained in wood are extracted, pressed in a state of moisture content of several percent or less, joined between pieces of wood, and air bubbles are discharged to form a carbonized biomass pellet.

   The embodiment of FIG. 2 is: (1) “reduced heating air” in which high-temperature air recovered from heat is burned from raw wood that has been processed into crushed raw materials to reduce the amount of oxygen in the air. After drying, (3) continuous extrusion pressurization is performed, and (4) after solidification, the product is cooled and heat recovery is air-cooled, heated by combustion using cooling air, and dried.

   The embodiment of FIG. 3 draws the exhaust heat (reduced heating air) of a closed material supply conveyor and an unnecessary wood piece incineration boiler supplied to a self-supporting heating and drying tank, takes out the desiccant, and continuously pressurizes to solidify and discharge the product. Later, exhaust heat is recovered from the product, pressurized air is injected from the sealed product storage tank, a series of necessary heat is supplied, heat exchange recovery and wood drying are performed, and the final exhaust air contains a large amount of moisture at almost normal temperature. Equipment that maximizes the thermal efficiency of the sealed structure to be discharged.

   In the embodiment of FIG. 4, exhaust heat recovery is performed from bottom to top over the lower middle part, and the recovered hot air is burned with wood chips or oil, if necessary, to produce reduced heated air with reduced oxygen content. Heated air is sent into the middle of the tank to ignite dry carbon and prevent rapid carbonization. From the bottom to the top, drying, necessary heating, and exhaust heat recovery cooling is a vertical heat exchange drying that uses natural fall of the material. Machine.

   Also, the drying and heat recovery conditions shown in FIG. 4 are that the lower cooling air temperature and exhaust steam temperature are about the same outside air temperature of 10-20 ° C. UP, and the temperature inside the tower is 200-230 ° C. in the center. Decreases in order from top to bottom. The drying cooling air speed is about 0.3-0.5m / sec, and even raw wood with a particle size of 1-2mm and moisture of 35% can reach 200 ° C in about 1 minute. The air velocity is determined by the raw material moisture content and size. Generally, a tower height of about 10 m is appropriate. However, all sealing is necessary due to the required performance as a reduction furnace.

   The plant location and use of these biomass pellets is optimal when they are installed in the log production area. In addition, when producing for forests near the consumption area and for production in a remote international cultivation area, if water resistance is sufficient, transportation and storage costs will be reduced, and the burden of international freight will be reduced. The same competitiveness will be offset by the costly use of thinned wood. In other words, in the area where labor force is effective, the efficiency of raw material cutting chip equipment affects important cost competitiveness.

℃ Celsius, represents temperature.
° Represents temperature.
MPa Megapascal (pressure unit)
True density Shows the apparent density relative to the apparent volume of crushed wood excluding moisture.
Moisture content Shows the moisture content (wt%) contained in wood.
Density Indicates the density after removing moisture from the wood. (Water is 1.0)
Compressibility Indicates the magnification at which the apparent volume is compressed to the contraction volume.

Claims (4)

   In the manufacturing method of biomass pellets, by using reduced heating dry gas such as combustion exhaust gas or air, the wood raw material is prevented from self-combustion (oxidation combustion) due to drying, and the ignition temperature is set to at least 220 ° C or higher. A method for producing biomass pellets using a reduced drying method that aims to improve dryness by compressing dry wood at 200 ° C or higher and making biomass pellets.    In the above-mentioned invention, the lower part of the sealed container in which the pulverized wood is introduced from the upper part of the sealed dry container, the dried wood is guided from the intermediate part, is pressed and heated and discharged under the intermediate part, and the discharged high temperature pellets are deposited. In order to obtain energy-saving effect, the three functions are connected with the purpose of cooling the exhausted high temperature pellets and reducing and drying the wood chip material containing moisture from the top by pumping cooling gas and air. Biomass pellet manufacturing method with characteristic structure.    In the equipment to implement the above-mentioned invention, the material is charged from the upper part of the sealed heating and drying furnace arranged vertically by the conveyor sealed from the material charging port, and the lower part of the wood pieces deposited in the furnace having the open moisture vapor discharge port from the top. Then, the heated heated air is drawn in, burns wood chips, heavy oil, LPG gas, etc., inserts the combustion gas into the lower part of the dry wood, reduces the heat, pulls out the dry wood piece from the lower part of the insert, and at least 5MPa Pressurize ~ 40MPa and hold pressure for at least 1 minute, discharge and accumulate in a closed container connected to the lower part of the drying furnace, take out the lower product in the container, and insert cooling air to heat the pellet Collect. Biomass pellet manufacturing equipment that can be connected to the bottom of the product take-out and storage sealed tank for cooling and cooling when necessary.    In the equipment for carrying out the above invention, a material having moisture is charged and deposited from the upper part of the drying tower tank installed vertically, dried from the bottom by heating with reducing hot air from the lower part, and the material heated and dried sufficiently is pressurized and solidified. The cooling air is discharged to the cooling tower tank, and the necessary drying energy is recovered by inserting cooling air into the heated solidified product deposited in the heat recovery tower tank from the bottom and sucking the air heated by the recovered heat from the middle part In addition, the additional energy necessary for drying the wood moisture of the raw material and, if necessary, the power generation to supply the power necessary for pressurization and the waste and A biomass pellet manufacturing facility that has a boiler facility that burns raw material scraps and, if necessary, has an exhaust heat recovery in-house power generation function.

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