JP7717106B2 - Black pellets and their manufacturing method - Google Patents

Description

This disclosure relates to black pellets and methods for producing them.

Since the Paris Climate Agreement in 2015, global efforts have been ongoing to limit the rise in the Earth's average temperature. As part of these efforts, there is a movement to reduce the use of fossil fuels, which are one of the causes of global warming, and to use new and renewable energy sources.

New and renewable energy refers to energy that is generated by converting existing fossil fuels or by converting renewable energy sources such as sunlight, water, geothermal heat, rainwater, and biological organisms. Unlike fossil fuels, new and renewable energy sources are renewable and inexhaustible, are environmentally friendly with fewer pollutants and carbon dioxide emissions, and are distributed more evenly across the globe than fossil fuels.

Among new renewable energies, forest biomass is known as a carbon-neutral energy source, minimizing climate change and replacing fossil fuels, making it an environmentally friendly renewable energy source. For example, wood pellets are made by turning the wood left over after felling trees, or forestry by-products that have not been contaminated with chemicals such as preservatives or paints, into sawdust and then compressing it to a certain size. In this regard, Korean Patent Registration No. 10-0878051 discloses technology for manufacturing wood pellets.

On the other hand, empty palm fruit bunches (EFBs) are the residue left over after the palm fruit bunches are removed in order to produce palm oil and other products from the palm fruit. Some of this palm waste, called empty palm fruit bunches, was used as livestock feed or compost, but the unused part had to be incinerated or disposed of.

However, palm empty fruit bunches have a high moisture content and are therefore prone to decay. When palm empty fruit bunches decay, they emit methane, a greenhouse gas, which can be problematic. However, various regulations currently make it difficult to incinerate palm empty fruit bunches, and waste disposal is extremely expensive. Therefore, from the perspectives of resource reuse and the environment, there is an urgent need to develop technology that can use discarded by-products as fuel.

Korean Patent No. 10-0878051

The technical concept of this invention is intended to solve the problems mentioned above, and its purpose is to provide a technology for producing fuel using biomass feedstock.

Another objective of the technical concept of this invention is to provide technology that allows by-products that have traditionally been incinerated or discarded to be reused as fuel.

The problems that the present invention aims to solve are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those with ordinary skill in the art to which the present invention pertains from the content described below.

To achieve this objective, as one embodiment of the present invention, a method for producing black pellets includes a pressing process for pressing biomass raw material; a volatile component removal process for removing volatile components from the compressed material obtained in the pressing process; a torrefaction process for torrefying the raw material from which the volatile components have been removed in the volatile component removal process; a crushing process for crushing the torrefied material obtained in the torrefaction process; a mixing process for adding a combustion additive and a binder to the crushed material obtained in the crushing process and mixing them; and a pelletizing process for forming the mixture obtained in the mixing process into pellets.

In the volatile component removal process, an inert gas is injected into the chamber in which the compressed material is placed, and the compressed material is heat-treated at 200-300°C while removing oxygen from the chamber, allowing the volatile components released from the compressed material to be discharged outside the chamber.

The biomass raw material may be at least one selected from wood by-products, palm empty fruit bunches (EFB), and palm kernel shells (PKS).

The combustion additive may be an aluminosilicate, and the ratio of the silicon dioxide content contained in the aluminosilicate divided by the aluminum oxide content contained in the aluminosilicate may be 0.65 to 1.85.

To achieve the above objective, in another embodiment of the present invention, the black pellets may be manufactured by the above-mentioned method for manufacturing black pellets.

To achieve the above objective, in yet another embodiment of the present invention, the black pellets may include semi-carbonized palm empty fruit bunches and aluminosilicate mixed with the semi-carbonized palm fruit bunches.

The ratio of the silicon dioxide content contained in the aluminosilicate divided by the aluminum oxide content contained in the aluminosilicate may be 0.65 to 1.85.

The calorific value of the black pellets may be 5,500 cal/g to 7,000 cal/g.

The black pellets may have an atomic ratio of hydrogen to carbon of 0.8 to 1.6 and an atomic ratio of oxygen to carbon of 0.2 to 0.8.

The solutions to the problems described above are merely exemplary and should not be construed as limiting the present invention. In addition to the exemplary embodiments described above, there may be additional embodiments as described in the drawings and detailed description of the invention.

As described above, according to various embodiments of the present invention, black pellets can be produced using biomass feedstock, making it possible to produce environmentally friendly fuel with a high calorific value.

In addition, black pellets according to various embodiments of the present invention can be mixed with coal in coal-fired power plants and can also be used as fuel in steel mills.

Furthermore, according to various embodiments of the present invention, when black pellets are burned, the aluminosilicate combustion additive can react with specific components (e.g., potassium, sodium, chlorine, etc.) contained in the biomass feedstock to produce a high-melting-point substance. This can improve thermal imbalance, slagging and fouling phenomena, and corrosion problems inside the boiler caused by specific components present in the biomass feedstock.

In particular, when producing black pellets from empty palm fruit bunches, it is possible to reduce waste disposal costs for empty palm fruit bunches and reduce methane gas generated by the decay of empty palm fruit bunches.When black pellets are burned, the potassium and chlorine contained in the empty palm fruit bunches are converted into high-melting-point substances by aluminosilicate, contributing to the complete combustion of fuel and preventing corrosion of metal surfaces, including the inner walls of boilers.

The effects of the various embodiments of the present invention are not limited to those mentioned above, and other effects not mentioned will be apparent to those skilled in the art from the claims.

1 is a flowchart schematically illustrating a method for manufacturing black pellets according to an embodiment of the present invention.

Preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings, but for the sake of brevity, previously known technical aspects will be omitted or simplified.

It should be noted that references herein to "one" or "an" embodiment of the present invention do not necessarily refer to the same embodiment, but rather to at least one.

In the following examples, singular expressions include plural expressions unless the context clearly dictates otherwise.

In the following examples, terms such as "include" or "have" mean that the features or components described in the specification are present, but do not preclude the possibility that one or more other features or components may also be added.

When alternative implementations are possible, certain steps may be performed out of the order shown. For example, two steps shown in succession may be performed substantially simultaneously, or may be performed in the reverse order from that shown. That is, the steps of any method described herein may be suitably performed in any order unless otherwise indicated in the specification or clearly contradicted by context.

As used herein, the term "black pellets" refers to pellets that are black in color, and can be given a black color through a torrefaction process during pellet production.

As used herein, the term "wood by-product" refers to a by-product that is produced for purposes other than those required for wood processing and is unavoidably generated during the wood processing process. For example, wood by-products can be waste wood, sawdust, or bark.

The method for producing black pellets according to one embodiment of the present invention will be described with reference to Figure 1, and for convenience, the description will be given in order.

1. Compression step <S101>
In this process, the biomass material can be compressed. For example, in this process, the biomass material is placed in a compressor and compressed under a certain pressure, thereby reducing the volume of the biomass material and increasing its density.

According to one embodiment, the biomass material to be compressed in this process may be at least one selected from wood by-products, palm empty fruit bunches, and palm kernel shells. The biomass material may be used alone or in combination of two or more.

2. Volatile component removal step <S102>
In this step, volatile components can be removed from the pressed product obtained in step S101. According to one embodiment, the pressed product is placed in a chamber, and the chamber is sealed. A chamber control unit opens an inlet of the chamber for a certain period of time to inject an inert gas (e.g., carbon dioxide), and then opens an outlet of the chamber to allow the gas in the chamber to flow out of the chamber, thereby removing oxygen present in the chamber.

In addition, when the oxygen concentration in the chamber is below a preset value, the chamber control unit can maintain the temperature inside the chamber at 200-300°C to heat-treat the compressed material and discharge volatile components from the compressed material to the outside of the chamber. Here, volatile components are components that can be removed from the compressed material by evaporating into gas when the compressed material is heated to 200°C or higher.

According to one embodiment, in this process, the chamber control unit maintains the temperature inside the chamber at 200-300°C for 10-15 minutes, then injects an inert gas into the chamber's inlet and opens the chamber's outlet, thereby discharging any volatile components remaining in the chamber to the outside of the chamber. After a certain amount of time has passed since the volatile components were discharged from the chamber, the chamber control unit can close the chamber's outlet.

3. Torrefaction step <S103>
In this step, the raw material from which volatile components have been removed in step S102 can be torrefied. For example, in this step, the chamber control unit can torrefy the raw material by maintaining the temperature inside the chamber at 300 to 400°C for 20 to 30 minutes while creating an oxygen-free or low-oxygen atmosphere inside the chamber. Here, an oxygen-free or low-oxygen atmosphere refers to a state in which an inert gas is supplied into the chamber at a constant flow rate, thereby keeping the oxygen concentration inside the chamber at a predetermined value or below (or a state in which an inert atmosphere with substantially no oxygen is present).

According to one specific example, the chamber control unit opens the chamber inlet for a certain period of time to inject an inert gas (e.g., carbon dioxide), and then opens the chamber outlet to allow the gas inside the chamber to flow out of the chamber, thereby removing oxygen present in the chamber and adjusting the oxygen concentration to a preset value or below. Only when the oxygen concentration is below the preset value can the chamber temperature be maintained at 300-400°C for 20-30 minutes, thereby carrying out the semi-carbonization process.

4. Crushing step <S104>
In this step, the semi-carbonized material semi-carbonized in step S103 can be pulverized. For example, in this step, the semi-carbonized material can be fed into a pulverizer and pulverized into particles having a certain average particle size range (for example, 0.1 to 5 mm).

5. Mixing step <S105>
In this process, a combustion additive and a binder may be added to and mixed with the pulverized material obtained in step S104. In one embodiment, the combustion additive may be an aluminosilicate. In this specification, the aluminosilicate refers to a combination of alumina (Al ₂ O ₃ ) and silica (SiO ₂ ). The aluminosilicate according to one embodiment may have a structure in which the number of silicon (Si) atoms relative to aluminum (Al) atoms is 1 to 5.

In one embodiment, the aluminosilicate content may be 0.1 to 10 parts by weight (e.g., 0.1 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight) per 100 parts by weight of the ground material.

Non-limiting examples of binders that can be added in this process include myristic acid, palmitic acid, oleic acid, and castor oil. According to one embodiment, the amount of binder added can be 0.1 to 15 parts by weight (e.g., 0.1 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, or 15 parts by weight) per 100 parts by weight of ground material.

6. Pelletization step <S106>
In this process, the mixture mixed in step S105 can be pelletized. According to one embodiment, the mixture mixed in step S105 can be fed into a pelletizer to produce pellets having a diameter of 4 to 10 mm and a length of 50 to 70 mm. According to one specific example, the mixture fed into the pelletizer can be extruded to have a diameter of 4 to 10 mm, and the extrudate can be cut to a predetermined length to produce pellets. Of course, the diameter and length of the pellets produced in this process can be adjusted as needed.

<Explanation of Black Pellets According to an Example>
The black pellets according to one embodiment are manufactured by mixing semi-carbonized material and aluminosilicate and pelletizing the mixture. The black pellets may include semi-carbonized material obtained by semi-carbonizing palm empty fruit bunches, and aluminosilicate mixed with the semi-carbonized material.

The aluminosilicate according to one embodiment may have a specific surface area of 100 to 180 m ² /g as measured in accordance with the International Organization for Standardization (ISO) 9277:2010. Specific examples of the specific surface area of the aluminosilicate include 100 m ² /g, 110 ^{m 2} /g, 120 m ² /g, 130 ^{m 2} /g, 140 ^{m 2} /g, 150 ^m 2 /g, 160 ^{m 2} /g, 170 ^{m 2} /g, and 180 ^{m 2} /g. The specific surface area of the aluminosilicate may be in a range of one or more of the above values and one or less of the above values.

For example, the specific surface area range of the aluminosilicate can be 100 m ² /g to 140 m ² /g, 105 ^{m 2} /g to 135 ^{m 2} /g, 110 m ² /g to 130 m ² /g, 115 m ² /g to 135 ^{m 2} /g, 120 m ² /g to 150 m ² /g, 125 m ² /g to 145 ^{m 2} /g, 100 ^{m 2} /g to 150 ^{m 2} /g, or 100 m ² /g to 180 m ² /g. The upper limit of the specific surface area of the aluminosilicate according to an embodiment is not particularly limited, and may be, for example, 300 m ² /g or less, 250 m ² /g or less, 200 ^{m 2} /g or less, 180 m ² /g or less, or 150 m ² /g or less.

When black pellets are produced using biomass raw materials such as wood by-products, palm empty fruit bunches, and palm kernel shells, the biomass raw materials may contain some alkaline components (e.g., K, Na, _K2O , _Na2O , etc.) or chlorine (Cl) due to their characteristics.

When black pellets are burned, alkaline components released from the biomass feedstock can adhere to the boiler's inner walls and heat exchanger, causing slagging and fouling. Chlorine released from the biomass feedstock reacts with alkaline components at high temperatures to form chlorides (e.g., KCl, NaCl, etc.), which can corrode the metal inside the boiler. In one embodiment, black pellets are produced by mixing aluminosilicate with the biomass feedstock, preventing slagging and fouling from occurring when the black pellets are burned and improving boiler corrosion problems.

According to one embodiment, the larger the specific surface area of the aluminosilicate, the easier it is to adsorb alkali components and chlorides generated during the combustion of black pellets, thereby effectively suppressing metal corrosion, slagging, and fouling.If the specific surface area of the aluminosilicate is less than 100 ^m2 /g, the efficiency of physically adsorbing and capturing alkali components and chlorides generated during the combustion of black pellets decreases, making it difficult to sufficiently control slagging and fouling, and there is a risk that chlorides will adhere to the inside of the boiler, causing corrosion of metal parts.

In one embodiment, the average particle size of the aluminosilicate may be 20 to 500 μm. Specific examples of the average particle size of the aluminosilicate include 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, and 500 μm. Of course, depending on the implementation, the average particle size of the aluminosilicate may be adjusted depending on the combustion conditions.

In one embodiment, the aluminosilicate may include silicon dioxide and aluminum oxide. The aluminosilicate according to one embodiment may also include unavoidable impurities as the balance excluding silicon dioxide and aluminum oxide.

According to one embodiment, the content of aluminum oxide contained in the aluminosilicate may be 20 to 60% by weight based on the total weight of the aluminosilicate. Specific examples of the aluminum oxide content include 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60% by weight. The aluminum oxide content may be greater than or equal to one of the above values and less than or equal to one of the above values.

For example, the aluminum oxide content range within the aluminosilicate may be 20% to 30% by weight, 30% to 40% by weight, 35% to 45% by weight, 40% to 50% by weight, or 20% to 60% by weight. Within this range, aluminum oxide according to one embodiment can effectively control the alkali and chloride content within the biomass feedstock.

If the aluminum oxide content in the aluminosilicate falls outside the range of 20-60% by weight, it will be difficult to effectively control the alkali components and chlorides released from the biomass raw material during the combustion of black pellets.

In one embodiment, the content of silicon dioxide contained in the aluminosilicate may be 40 to 80% by weight based on the total weight of the aluminosilicate. Specific examples of the content of silicon dioxide include 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80% by weight. The content of silicon dioxide may be greater than or equal to one of the above values and less than or equal to one of the above values.

For example, the content range of silicon dioxide contained in the aluminosilicate may be 40% to 50% by weight, 50% to 60% by weight, 55% to 65% by weight, 60% to 70% by weight, 55% to 70% by weight, or 40% to 80% by weight. Silicon dioxide according to one embodiment can effectively control the alkali components and chlorides contained in the biomass feedstock within this range. If the silicon dioxide contained in the aluminosilicate is outside the 40 to 80% by weight range, it is difficult to effectively control the alkali components and chlorides released from the biomass feedstock during the combustion of black pellets.

According to one embodiment, when the black pellets are burned, the aluminosilicate chemically reacts with the alkali components and chlorides contained in the biomass feedstock, converting the alkali components and chlorides released from the biomass feedstock into at least one of kalsilite (KAlSiO ₄ ) and lucite (KAlSi ₂ O ₆ ).

In other words, the alkaline components and chlorides generated during the combustion of black pellets react with aluminosilicates and are converted into kalsilite, which has a melting point of over 1600°C, or lucite, which has a melting point of over 1500°C. This improves the problems of slagging, fouling, and condensation that previously occurred when alkaline components melted in boilers, and prevents metal corrosion caused by chlorides.

Meanwhile, according to one embodiment, the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate may be 0.65 to 1.85. In one specific example, if the silicon dioxide content in the aluminosilicate is 48 parts by weight and the aluminum oxide content in the aluminosilicate is 42 parts by weight, the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate may be 1.14.

Specific examples include the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate: 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8, 0.81, 0.8 2, 0.84, 0.86, 0.88, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1. 17, 1.18, 1.19, 1.2, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, 1.3, 1.31, 1.32, 1.34, 1.36, 1.38, 1.4, 1.42, 1.44, 1.46, 1.48, 1.5, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, The ratio may be 1.57, 1.58, 1.59, 1.6, 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, 1.7, 1.71, 1.72, 1.73, 1.74, 1.75, 1.76, 1.77, 1.78, 1.79, 1.8, 1.81, 1.82, 1.83, 1.84, or 1.85. In addition, the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate may be in a range of one or more of the above values and one or less of the above values.

For example, the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate may be in the range of 0.65 to 1.85, 0.78 to 1.2, 0.58 to 1.2, 0.98 to 1.2, 0.9 to 1.2, 0.9 to 1.3, 1 to 1.2, 1 to 1.4, 1.18 to 1.58, 1.2 to 1.58, 1.38 to 1.58, or 0.78 to 1.58. According to one embodiment, when the ratio of the silicon dioxide content to the aluminum oxide content in the aluminosilicate is within this range, slagging and fouling caused by alkaline components in the biomass feedstock can be effectively suppressed.

If the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate falls outside the range of 0.65 to 1.85, the efficiency of reaction with the alkaline components released from the biomass feedstock to produce high-melting-point substances (e.g., kalsilite, lucite, etc.) decreases, making it difficult to prevent slagging and fouling.

According to one embodiment, X-ray fluorescence spectroscopy can be used to determine the weights of silicon dioxide and aluminum oxide contained in the aluminosilicate. Therefore, the ratio of the silicon dioxide content in the aluminosilicate divided by the aluminum oxide content in the aluminosilicate can be calculated.

Meanwhile, according to one embodiment, when the aluminosilicate is heated from 400°C to 800°C, the weight loss rate may be 5% or less, 4.5% or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2% or less, 1.5% or less, 1% or less, 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less. For example, when the temperature is increased from 400°C to 800°C at a rate of 10°C per minute, the weight loss rate of the aluminosilicate may be 5% or less. Here, the weight loss rate of the aluminosilicate can be calculated using the following equation 1.

[Equation 1]
Weight loss rate of aluminosilicate (%)=(A−B)/A*100
(where A is the weight of the aluminosilicate at 400°C and B is the weight of the aluminosilicate at 800°C)

The lower limit of the weight loss rate of the aluminosilicate according to one embodiment is not particularly limited, but may be, for example, 0.001% or more, 0.01% or more, or 0.05% or more.

Unlike kaolin (e.g., kaolinite, halloysite, etc.), the aluminosilicate according to one embodiment does not contain water of crystallization within the aluminosilicate. Therefore, the phenomenon of the water of crystallization evaporating at high temperatures and causing a decrease in the total weight of the aluminosilicate hardly occurs, and the weight loss rate is less than 5% at temperatures between 400 and 800°C.

In contrast, kaolin's specific surface area may become larger than at room temperature as the water of crystallization contained within it evaporates at temperatures between 400 and 800°C. However, since kaolin's specific surface area does not increase until it reaches the temperature at which the water of crystallization evaporates, it is difficult to quickly adsorb and remove alkaline components originating from biomass raw materials.

However, the aluminosilicate according to one embodiment does not contain crystal water inside and can maintain a specific surface area (e.g., 100-180 ^m2 /g) at 400-800°C similar to that at room temperature (e.g., 20-25°C), so it can adsorb and remove alkaline components more quickly than kaolin.

In one embodiment, the calorific value of the black pellets may be 5500 cal/g to 7000 cal/g. Specific examples of the calorific value of the black pellets include 5500 cal/g, 5600 cal/g, 5700 cal/g, 5800 cal/g, 5900 cal/g, 6000 cal/g, 6100 cal/g, 6200 cal/g, 6300 cal/g, 6400 cal/g, 6500 cal/g, 6600 cal/g, 6700 cal/g, 6800 cal/g, 6900 cal/g, and 7000 cal/g. The calorific value of the black pellets may range from one or more of the above values to one or less of the above values.

For example, the calorific value of black pellets may range from 5500 cal/g to 7000 cal/g, 6000 cal/g to 7000 cal/g, 5500 cal/g to 6000 cal/g, or 6500 cal/g to 7000 cal/g. Black pellets according to one embodiment exhibit excellent combustion efficiency within this calorific value range. If the calorific value of black pellets is less than 5500 cal/g, combustion efficiency decreases, and attempting to produce black pellets with a calorific value exceeding 7000 cal/g increases the complexity of the process and increases production costs.

In one embodiment, the black pellets may have an atomic ratio of hydrogen to carbon (atomic H/C ratio) of 0.8 to 1.6. Specific examples include the atomic ratio of hydrogen to carbon of the black pellets being 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or 1.6. The atomic ratio of hydrogen to carbon of the black pellets may also be in a range between one or more of the above values and one or less of the above values.

For example, the atomic ratio of hydrogen to carbon in the black pellets may be in the range of 0.8 to 1.6, 0.8 to 1, 1 to 1.6, 1 to 1.5, 0.9 to 1.3, or 1 to 1.4. When the atomic ratio of hydrogen to carbon in the black pellets according to one embodiment is within this range, excellent combustion efficiency is exhibited. If the atomic ratio of hydrogen to carbon in the black pellets is less than 0.8, the combustion efficiency is excellent, but the pellet manufacturing process may become complicated and the manufacturing costs may increase. If the atomic ratio exceeds 1.6, the combustion efficiency may decrease.

In one embodiment, the black pellets may have an atomic ratio of oxygen to carbon (atomic O/C ratio) of 0.2 to 0.8. Specific examples include the atomic ratio of oxygen to carbon of the black pellets being 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8. The atomic ratio of oxygen to carbon of the black pellets may also be in a range of one or more of the above values and one or less of the above values.

For example, the atomic ratio of oxygen to carbon in the black pellets may be in the range of 0.2 to 0.8, 0.3 to 0.7, 0.4 to 0.6, or 0.2 to 0.5. When the atomic ratio of oxygen to carbon in the black pellets according to one embodiment is within this range, excellent combustion efficiency is exhibited. If the atomic ratio of oxygen to carbon in the black pellets is less than 0.2, the combustion efficiency is excellent, but the pellet manufacturing process may become complicated and manufacturing costs may increase. If the atomic ratio exceeds 0.8, the combustion efficiency may decrease.

In one embodiment, the atomic ratios (atomic H/C ratio and atomic O/C ratio) of the black pellets can be quantitatively measured using an elemental analyzer (for example, Thermo Scientific's Flash-EA1112).

The present invention will be described in more detail below based on specific examples and experimental examples. The following examples and experimental examples are merely illustrative examples intended to aid in understanding the present invention, and do not limit the scope of the present invention.

Production of Black Pellets by Examples and Comparative Examples <Examples 1 to 5 and Comparative Examples 1 and 2>
1,000 kg of empty palm fruit bunches were placed in a press and pressed, followed by loading the pressed material into a chamber. The chamber was sealed, and carbon dioxide, an inert gas, was injected through the chamber inlet at a flow rate of 1,000 sccm. The outlet was then opened for 10 minutes to allow the gas inside the chamber to be discharged to the outside of the chamber. The pressed material was heat-treated for 10 to 15 minutes while maintaining a carbon dioxide atmosphere (oxygen-free conditions) inside the chamber and setting the internal temperature of the chamber to 200 to 300°C. After the heat treatment was completed, carbon dioxide was injected through the chamber inlet at a flow rate of 1,000 sccm, and the outlet was opened to allow the volatile components remaining in the chamber to be discharged to the outside of the chamber for 10 minutes. The raw material was then torn into a semi-carbonized material by maintaining the internal temperature of the chamber at 300 to 400°C for 20 to 30 minutes while maintaining the internal carbon dioxide atmosphere. The semi-carbonized material was then loaded into a grinder and crushed to particles of 0.1 to 5 mm. Thereafter, 100 kg of the pulverized material, 10 kg of aluminosilicate, and 10 kg of binder (myristic acid) were mixed in a mixer and stirred at 300 rpm for 10 hours. After stirring was completed, the mixture was fed into a pellet molding machine to produce black pellets with a diameter of 6 mm and a length of 5 to 7 cm.

The weights of silicon dioxide and aluminum oxide in the aluminosilicates of the Examples and Comparative Examples added to the mixer during the production of black pellets were measured using an X-ray fluorescence spectrometer (Rigaku's ZSX Primus II), and the ratios obtained by dividing the silicon dioxide content in the aluminosilicate by the aluminum oxide content in the aluminosilicate were calculated and are shown in Table 1 below.

Experiments on Slagging and Fouling Suppression of Black Pellets in Examples and Comparative Examples <Examples 1 to 5 and Comparative Examples 1 and 2>
The slagging and fouling suppression performance of the examples and comparative examples was compared by feeding and burning black pellets into a pilot test machine modeled after a circulating fluidized bed boiler used in thermal power plants. The black pellets were fed into the test machine at a rate of 2.5 kg/hr for three hours, and the average temperatures of the combustion furnace and measurement load cell were maintained at 850°C and 600°C, respectively, during the pilot test. After the test was completed, the weight change of the load cell was measured to determine the weight of the slagging and fouling (i.e., the alkali components contained in the biomass feedstock melted and solidified on the surface of the load cell together with ash particles) formed on the surface of the load cell. The results are shown in Table 2.

Referring to Table 2, it can be seen that Examples 1 to 5, in which the ratio of the silicon dioxide content contained in the aluminosilicate divided by the aluminum oxide content contained in the aluminosilicate is within the range of 0.65 to 1.85, exhibited relatively less slagging and fouling than Comparative Examples 1 and 2. In other words, the black pellets of Examples 1 to 5 effectively control the alkaline components contained in the biomass feedstock during combustion, thereby suppressing the occurrence of slagging and fouling, and preventing the alkaline components from reacting with chlorine to form chlorides, thereby preventing chlorides from adhering to the inner walls and metal parts of the boiler and causing corrosion.

Measurement of specific surface area by BET method <Examples 1 to 5>
0.1 g of the aluminosilicate sample used in each example was pretreated at 100°C to remove surface water from the sample, and then the specific surface area of each sample was measured three times using a BELSORP-max II instrument manufactured by MicrotracBEL in accordance with the standard analytical method ISO 9277:2010, and the average values were listed in Table 3 below.

Measurement of Weight Loss Rate <Examples 1 to 5>
200 mg of an aluminosilicate sample used in each example was placed in a thermogravimetric-differential scanning calorimeter (SDT Q600, TA Instruments) and heated from room temperature (25°C) to 1,000°C at a rate of 10°C per minute. The weights of the aluminosilicate were measured at 400°C and 800°C, and the weight loss rate for each sample was calculated using Equation 1 above. The results are shown in Table 4 below.

As described above, according to various embodiments of the present invention, black pellets can be produced using biomass feedstock, making it possible to produce environmentally friendly fuel with a high calorific value.

In addition, black pellets according to various embodiments of the present invention can be mixed with coal in coal-fired power plants and can also be used as fuel in steel mills.

Furthermore, according to various embodiments of the present invention, when black pellets are burned, the aluminosilicate combustion additive can react with specific components (e.g., potassium, sodium, chlorine, etc.) contained in the biomass feedstock to produce a high-melting-point substance. This can improve thermal imbalance, slagging, fouling, and corrosion problems inside the boiler caused by specific components present in the biomass feedstock.

In particular, when black pellets are produced from empty palm fruit bunches, it is possible to reduce waste disposal costs for empty palm fruit bunches and reduce the methane gas generated by the decay of empty palm fruit bunches. Furthermore, when black pellets are burned, the potassium and chlorine contained in the empty palm fruit bunches are converted into high-melting-point substances by aluminosilicate, contributing to the complete combustion of fuel and preventing corrosion of metal surfaces, including the inner walls of boilers.

In addition, according to various embodiments of the present invention, the time and energy required for the torrefaction process can be reduced by removing volatile components from the compressed material through a volatile component removal process before the torrefaction process. Furthermore, since carbon dioxide can be injected into the chamber during the volatile component removal process and torrefaction process to create an oxygen-free environment inside the chamber, the torrefaction process can be performed at a lower cost than using other inert gases (e.g., nitrogen, argon).

In addition, according to various embodiments of the present invention, slagging and fouling caused by alkaline components can be suppressed by controlling the alkaline components contained in biomass raw materials without using kaolin.

Furthermore, according to various embodiments of the present invention, the aluminosilicate mixed with the semi-carbide has a small weight loss rate at high temperatures, making it easy to set the amount of aluminosilicate added. Furthermore, since there is little loss due to ignition loss, the alkali content can be controlled with a relatively small amount compared to kaolin.

In addition, according to various embodiments of the present invention, since the aluminosilicate does not contain water of crystallization, it can maintain a specific surface area of approximately 100 to 180 m ² /g at room temperature (e.g., 20 to 25°C) without heat-treating the aluminosilicate at a high temperature of 400 to 800°C. Due to the large specific surface area, it can physically adsorb and remove alkali components that melt when black pellets are burned, thereby preventing slagging and fouling.

If the aluminosilicate contains water of crystallization, the specific surface area of the aluminosilicate can be increased only by removing the water of crystallization through heat treatment at high temperatures. However, according to various embodiments of the present invention, the aluminosilicate has a high specific surface area without the need to separately remove the water of crystallization, which has the advantage that the alkaline components can be controlled through a rapid adsorption reaction when the black pellets are burned.

As explained above, the present invention has been specifically described based on the embodiments, but the above-described embodiments merely illustrate preferred examples of the present invention, and the present invention should not be understood as being limited to the above-described embodiments. The scope of the present invention should be understood as the scope of the claims set forth below and their equivalents.

Claims (5)

A method for producing black pellets for suppressing slagging and fouling in a combustion furnace of a boiler, which are used during combustion in the combustion furnace of a boiler,
a compressing step of compressing the biomass raw material;
a volatile component removal step of removing volatile components from the compressed product obtained in the compression step;
a semi-carbonization process for semi-carbonizing the raw material from which the volatile components have been removed in the volatile component removal process;
a pulverization step of pulverizing the semi-carbonized material obtained in the semi-carbonization step;
a mixing step of adding a combustion additive and a binder to the pulverized material obtained in the pulverization step and mixing the pulverized material;
a pelletizing step of forming the mixture mixed in the mixing step into pellets;
Including,
the combustion additive is an aluminosilicate;
The specific surface area of the aluminosilicate is 100 to 180 m ² /g at room temperature without heat treatment of the aluminosilicate;
The method for producing black pellets is characterized in that the average particle size of the aluminosilicate is 70 to 500 μm. The method for producing black pellets described in claim 1, characterized in that in the volatile component removal process, an inert gas is injected into a chamber in which the compressed material is placed, the compressed material is heat-treated at 200 to 300°C while removing oxygen present in the chamber, and the volatile components released from the compressed material are discharged to the outside of the chamber. The method for producing black pellets described in claim 1, characterized in that the biomass raw material is at least one selected from the group consisting of wood by-products, palm empty fruit bunches (EFB), and palm kernel shells (PKS). The method for producing black pellets described in claim 1, wherein the ratio of the silicon dioxide content contained in the aluminosilicate divided by the aluminum oxide content contained in the aluminosilicate is 0.65 to 1.85. Black pellets produced by the manufacturing method described in any one of claims 1 to 4.