Anti-caking biomass fuel and method for preparing the same

Abstract

The application discloses a biomass fuel with anti-slagging and a preparation method thereof, and belongs to the technical field of biomass fuels. The biomass fuel is prepared by using agricultural wastes such as crop straws and branches, and an anti-slagging agent composed of magnesium carbonate, aluminum oxide and calcium carbonate is adopted, wherein the magnesium carbonate reduces the adhesion between particles by physically blocking and adsorbing moisture, the aluminum oxide improves the ash melting point and inhibits sintering through chemical reaction, the calcium carbonate further improves the ash melting point and fixes potassium by generating calcium oxide through decomposition, and the porous ceramic is combined, the pore structure of the porous ceramic can increase the contact area of the ceramic and the ash generated by biomass combustion, and the capture and fixation capacity of alkali metals and other components in the ash is improved, so that the slagging rate is effectively reduced, and finally the biomass fuel with low slagging rate is obtained.

Description

Technical Field

[0001] This invention belongs to the field of biomass fuel technology, and particularly relates to an anti-caking biomass fuel and its preparation method. Background Technology

[0002] Biomass fuel refers to fuel made from agricultural production residues such as crop straw. It is a highly efficient way to utilize crop straw, with advantages such as high density, easy combustion, high calorific value, and easy storage. Furthermore, its net CO2 emissions during use are close to zero, and NO... X It also has low SO2 emissions, which can effectively reduce straw burning in rural areas and improve the atmospheric environment.

[0003] However, biomass fuel exhibits significant slagging during actual combustion, causing severe corrosion to boilers and affecting their safe and stable operation. Slagging refers to two phenomena: first, when solid or ash-containing liquid fuels burn in a boiler, high levels of alkali metals and other minerals are mixed into fly ash particles and adhere to various heating surfaces of the boiler; second, severe slagging forms at the bottom of the boiler after biomass fuel combustion. Therefore, how to utilize crop straw to prepare biomass fuels with anti-slagging properties has become a pressing technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an anti-caking biomass fuel and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides an anti-caking biomass fuel, comprising the following raw materials in parts by weight: 90-120 parts of crop straw, 30-50 parts of branches, 0.9-6 parts of anti-caking agent, and 0.2-0.35 parts of porous ceramics;

[0007] The anti-slagging agent comprises the following raw materials by weight percentage: 15-25% magnesium carbonate, 20-30% alumina, and 45-65% calcium carbonate;

[0008] The raw materials for preparing the porous ceramics include steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate, and sodium borate.

[0009] Technical Principle: This invention utilizes agricultural waste such as crop straw and branches to prepare biomass fuel, and employs an anti-slagging agent composed of magnesium carbonate, alumina, and calcium carbonate. Magnesium carbonate reduces particle adhesion through physical barrier and moisture adsorption, alumina increases the ash melting point and inhibits sintering through chemical reaction, and calcium carbonate further increases the ash melting point and fixes potassium by decomposing to produce calcium oxide. Simultaneously, porous ceramics are combined, whose pore structure increases the contact area between the ceramics and the ash produced by biomass combustion, improving the capture and fixation capacity of alkali metals and other components in the ash, thereby effectively reducing the slagging rate and ultimately obtaining a biomass fuel with a low slagging rate.

[0010] Furthermore, the crop straw is selected from at least one of corn straw, sorghum straw, and rice straw.

[0011] Furthermore, the branches are selected from at least one of peach branches, apple branches, and pear branches.

[0012] Furthermore, the mass ratio of the steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate is (30~45):(40~55):(65~85):(15~25):(5~8):(6~12).

[0013] Furthermore, the raw materials for preparing the porous ceramic also include a dispersant; the dispersant is selected from sodium polyphosphate, ammonium polyacrylate or ammonium oxalate; the amount of the dispersant is 0.1~0.3% of the mass of fly ash.

[0014] Furthermore, the preparation method of the porous ceramic includes the following steps: mixing steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate evenly to obtain a mixture; adding water and dispersant to the mixture, mixing evenly, and then molding and sintering to obtain the porous ceramic.

[0015] Furthermore, the molding temperature is 100~150℃, and the molding time is 2~3 hours.

[0016] Furthermore, the sintering temperature is 1250~1350℃, the sintering holding time is 2~3h, and the rate of heating to the sintering temperature is 2~5℃ / min.

[0017] The present invention also provides a method for preparing anti-caking biomass fuel according to the above technical solution, comprising the following steps: crushing crop straw and branches and sieving them, then mixing them with an anti-caking agent and porous ceramics, and then pressing them to obtain the anti-caking biomass fuel.

[0018] Furthermore, the sieving is performed through a 1-2 mm sieve; and / or, the temperature of the pressure molding is room temperature, the pressure of the pressure molding is 50-80 MPa, and the pressure molding time is 50-100 s.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects:

[0020] This invention utilizes agricultural waste such as crop straw and branches to prepare biomass fuel, and uses industrial waste such as steel slag, bauxite tailings, and fly ash as main raw materials to prepare porous ceramics, realizing the recycling of agricultural and industrial waste. Moreover, the raw materials used are widely available and inexpensive, reducing the production cost of biomass fuel.

[0021] The anti-slagging biomass fuel provided by this invention can significantly reduce slagging rate, improve combustion efficiency, and reduce environmental pollution. It not only integrates various agricultural and industrial wastes, but also plays a positive role in forming solid biomass fuel and reducing the overall cost of biomass energy. Detailed Implementation

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0024] This invention provides an anti-caking biomass fuel, comprising the following raw materials in parts by weight: 90-120 parts of crop straw, 30-50 parts of branches, 0.9-6 parts of anti-caking agent, and 0.2-0.35 parts of porous ceramics; more preferably, 93-115 parts of crop straw, 33-46 parts of branches, 1.2-4.8 parts of anti-caking agent, and 0.2-0.3 parts of porous ceramics.

[0025] In a preferred embodiment, the crop straw is selected from at least one of corn straw, sorghum straw and rice straw, and is more preferably corn straw and / or rice straw.

[0026] In a preferred embodiment, the branches are selected from at least one of peach branches, apple branches, and pear branches, and more preferably at least one of apple branches and / or pear branches. This invention utilizes agricultural waste such as straw and branches, achieving waste recycling while simultaneously yielding high-value products.

[0027] In a preferred embodiment, the anti-slagging agent comprises the following raw materials by weight percentage: 15-25% magnesium carbonate, 20-30% alumina, and 45-65% calcium carbonate; more preferably: 18-22% magnesium carbonate, 24-28% alumina, and 48-55% calcium carbonate. In the anti-slagging agent of this invention, magnesium carbonate reduces particle adhesion through physical barrier and moisture adsorption; alumina increases the ash melting point and inhibits sintering through chemical reaction; and calcium carbonate further increases the ash melting point and fixes potassium through the decomposition of calcium oxide. The combined effect of these components exhibits excellent anti-slagging performance in biomass fuels, significantly reducing slagging rate, improving combustion efficiency, and reducing environmental pollution.

[0028] In a preferred embodiment, the method for preparing the anti-slagging agent includes the following steps: mixing calcium carbonate and aluminum oxide evenly, then adding magnesium oxide and mixing evenly to obtain the anti-slagging agent. The particle size of the anti-slagging agent obtained after mixing should be less than 1 mm to ensure thorough mixing with biomass raw materials.

[0029] In a preferred embodiment, the raw materials for preparing the porous ceramic include steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate, and sodium borate; the mass ratio of the steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate, and sodium borate is (30~45):(40~55):(65~85):(15~25):(5~8):(6~12), more preferably (32~42):(45~53):(68~80):(17~22):(6~8):(7~10); the average particle size of the alumina powder is 300~500 nm. This invention uses industrial waste such as steel slag, bauxite tailings, and fly ash as main raw materials. These raw materials contain abundant silicates, aluminates, and other components, which can form a stable ceramic structure through high-temperature sintering. Alumina powder can react with the components in steel slag to generate highly active products, thereby forming structures such as platy calcium aluminum feldspar, increasing the porosity of porous ceramics. Calcium carbonate, as a foaming agent, can decompose at high temperatures to generate gas and form a uniform pore structure. Sodium borate, as a sintering aid, can lower the sintering temperature and improve the strength of the ceramic, ultimately obtaining porous ceramics that can capture and fix alkali metals and other components in the ash, thereby reducing the slagging rate of biomass fuel.

[0030] In a preferred embodiment, the raw materials for preparing the porous ceramic further include a dispersant; the dispersant is selected from sodium polyphosphate, ammonium polyacrylate or ammonium oxalate; the amount of the dispersant is 0.1~0.3% of the mass of fly ash.

[0031] In a preferred embodiment, the method for preparing the porous ceramic includes the following steps: mixing steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate evenly to obtain a mixture; adding water and a dispersant to the mixture, mixing evenly, and then molding and sintering to obtain the porous ceramic.

[0032] In a preferred embodiment, the steel slag, bauxite tailings and fly ash are further subjected to crushing and screening steps before mixing; the mesh size of the screen used for screening is 300-500 mesh.

[0033] In a preferred embodiment, the amount of water added is 1 to 5% of the mass of fly ash.

[0034] In a preferred embodiment, the molding temperature is 100~150℃, more preferably 110~130℃; the molding time is 2~3h, more preferably 2~2.5h.

[0035] In a preferred embodiment, the sintering temperature is 1250~1350℃, more preferably 1280~1320℃; the sintering holding time is 2~3h, more preferably 2~2.5h; and the rate of heating to the sintering temperature is 2~5℃ / min.

[0036] The present invention also provides a method for preparing anti-caking biomass fuel according to the above technical solution, comprising the following steps: crushing crop straw and branches and sieving them, then mixing them with an anti-caking agent and porous ceramics, and then pressing them to obtain the anti-caking biomass fuel.

[0037] In a preferred embodiment, the sieving is performed through a 1-2 mm sieve.

[0038] In a preferred embodiment, the step of adding water to adjust the moisture content of the mixture to 8-10% before pressure molding is further included.

[0039] In a preferred embodiment, the temperature of the pressure molding is room temperature, the pressure of the pressure molding is 50~80MPa, and the pressure molding time is 50~100s.

[0040] In a preferred embodiment, the process after pressure molding further includes a drying step; the drying temperature is 100~120℃, and the drying time is 1~2 hours.

[0041] Unless otherwise specified, all parts in this invention represent "parts by weight".

[0042] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0043] Example 1

[0044] A method for preparing anti-caking biomass fuel, comprising the following steps:

[0045] (1) Mix calcium carbonate and aluminum oxide evenly, then add magnesium oxide and mix evenly to obtain an anti-slagging agent; wherein, the mass content of magnesium carbonate in the anti-slagging agent is 18%, the mass content of aluminum oxide is 28%, and the mass content of calcium carbonate is 54%;

[0046] (2) After crushing steel slag, bauxite tailings and fly ash, the mixture is passed through a 500-mesh sieve. Then, the sieved steel slag, bauxite tailings and fly ash are mixed evenly with alumina powder, calcium carbonate and sodium borate to obtain a mixture. Water and ammonium polyacrylate are added to the mixture and mixed evenly to obtain a slurry. The slurry is injected into a spherical mold with a diameter of 2 mm and kept at 110℃ for 2 h. Then, the temperature is increased to 1280℃ at a heating rate of 2℃ / min and kept at 2.5 h to obtain porous ceramics. The mass ratio of steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate is 35:48:72:25:6:11. The average particle size of alumina powder is 300 nm. The amount of water added is 3% of the mass of fly ash and the amount of ammonium polyacrylate added is 0.1% of the mass of fly ash.

[0047] (3) After crushing 90 parts of corn stalks and 35 parts of peach branches, they were passed through a 2mm sieve and then mixed evenly with 2 parts of the anti-caking agent prepared in step (1) and 0.35 parts of the porous ceramic prepared in step (2) to obtain a mixture. Water was added to adjust the moisture content of the mixture to 8%, and then it was pressed at 80MPa for 100s and then dried at 110℃ for 1h to obtain anti-caking biomass fuel.

[0048] Example 2

[0049] A method for preparing anti-caking biomass fuel, comprising the following steps:

[0050] (1) Mix calcium carbonate and aluminum oxide evenly, then add magnesium oxide and mix evenly to obtain an anti-slagging agent; wherein, the mass content of magnesium carbonate in the anti-slagging agent is 20%, the mass content of aluminum oxide is 24%, and the mass content of calcium carbonate is 56%;

[0051] (2) After crushing steel slag, bauxite tailings and fly ash, the mixture is passed through a 500-mesh sieve. Then, the sieved steel slag, bauxite tailings and fly ash are mixed evenly with alumina powder, calcium carbonate and sodium borate to obtain a mixture. Water and ammonium polyacrylate are added to the mixture and mixed evenly to obtain a slurry. The slurry is injected into a spherical mold with a diameter of 2 mm and kept at 130℃ for 2 h. Then, the temperature is increased to 1320℃ at a heating rate of 5℃ / min and kept at 1320℃ for 2 h to obtain porous ceramics. The mass ratio of steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate is 45:40:65:15:8:7. The average particle size of alumina powder is 500 nm. The amount of water added is 2% of the mass of fly ash and the amount of ammonium polyacrylate added is 0.1% of the mass of fly ash.

[0052] (3) After crushing 120 parts of rice straw and 40 parts of pear branches, pass them through a 2mm sieve and mix them evenly with 6 parts of the anti-caking agent prepared in step (1) and 0.2 parts of the porous ceramic prepared in step (2) to obtain a mixture. Add water to adjust the moisture content of the mixture to 8%, then press it at 50MPa for 90s, and then dry it at 100℃ for 1.5h to obtain anti-caking biomass fuel.

[0053] Example 3

[0054] A method for preparing anti-caking biomass fuel, comprising the following steps:

[0055] (1) Mix calcium carbonate and aluminum oxide evenly, then add magnesium oxide and mix evenly to obtain an anti-slagging agent; wherein, the mass content of magnesium carbonate in the anti-slagging agent is 22%, the mass content of aluminum oxide is 30%, and the mass content of calcium carbonate is 48%;

[0056] (2) After crushing steel slag, bauxite tailings and fly ash, the mixture is passed through a 500-mesh sieve. Then, the sieved steel slag, bauxite tailings and fly ash are mixed evenly with alumina powder, calcium carbonate and sodium borate to obtain a mixture. Water and ammonium polyacrylate are added to the mixture and mixed evenly to obtain a slurry. The slurry is injected into a spherical mold with a diameter of 2 mm and kept at 115℃ for 2.5 h. Then, the temperature is increased to 1300℃ at a heating rate of 3℃ / min and kept at 1300℃ for 2.5 h to obtain porous ceramics. The mass ratio of steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate is 42:53:76:21:6:11. The average particle size of alumina powder is 500 nm. The amount of water added is 3% of the mass of fly ash and the amount of ammonium polyacrylate added is 0.2% of the mass of fly ash.

[0057] (3) After crushing 115 parts of corn stalks and 45 parts of peach branches, the mixture is passed through a 2mm sieve and then mixed evenly with 3.6 parts of the anti-caking agent prepared in step (1) and 0.2 parts of the porous ceramic prepared in step (2) to obtain a mixture. Water is added to adjust the moisture content of the mixture to 8%, and then it is pressed at 70MPa for 60s, and then dried at 105℃ for 1h to obtain anti-caking biomass fuel.

[0058] Comparative Example 1

[0059] A method for preparing anti-caking biomass fuel, comprising the following steps:

[0060] (1) Mix calcium carbonate and aluminum oxide evenly, then add magnesium oxide and mix evenly to obtain an anti-slagging agent; wherein, the mass content of magnesium carbonate in the anti-slagging agent is 22%, the mass content of aluminum oxide is 30%, and the mass content of calcium carbonate is 48%;

[0061] (2) After crushing 115 parts of corn stalks and 45 parts of peach branches, the mixture was passed through a 2mm sieve and then mixed evenly with 3.6 parts of the anti-caking agent prepared in step (1) to obtain a mixture. Water was added to adjust the moisture content of the mixture to 8%, and then it was pressed at 70MPa for 60s and then dried at 105℃ for 1h to obtain anti-caking biomass fuel.

[0062] Comparative Example 2

[0063] A method for preparing anti-caking biomass fuel, comprising the following steps:

[0064] (1) After crushing steel slag, bauxite tailings and fly ash, the mixture is passed through a 500-mesh sieve. Then, the sieved steel slag, bauxite tailings and fly ash are mixed evenly with alumina powder, calcium carbonate and sodium borate to obtain a mixture. Water and ammonium polyacrylate are added to the mixture and mixed evenly to obtain a slurry. The slurry is injected into a spherical mold with a diameter of 2 mm and kept at 115℃ for 2.5 h. Then, the temperature is increased to 1300℃ at a heating rate of 3℃ / min and kept at 1300℃ for 2.5 h to obtain porous ceramics. The mass ratio of steel slag, bauxite tailings, fly ash, alumina powder, calcium carbonate and sodium borate is 42:53:76:21:6:11. The average particle size of alumina powder is 500 nm. The amount of water added is 3% of the mass of fly ash and the amount of ammonium polyacrylate added is 0.2% of the mass of fly ash.

[0065] (2) After crushing 115 parts of corn stalks and 45 parts of peach branches, the mixture was passed through a 2mm sieve and then mixed evenly with 0.2 parts of porous ceramic prepared in step (1) to obtain a mixture. Water was added to adjust the moisture content of the mixture to 8%, and then it was pressed at 70MPa for 60s and then dried at 105℃ for 1h to obtain anti-caking biomass fuel.

[0066] Comparative Example 3

[0067] A method for preparing anti-caking biomass fuel differs from Example 3 in that step (2) is as follows: steel slag, bauxite tailings and fly ash are crushed and passed through a 500-mesh sieve, and then the sieved steel slag, bauxite tailings and fly ash are mixed evenly to obtain a mixture; water and ammonium polyacrylate are added to the obtained mixture and mixed evenly to obtain a slurry; the obtained slurry is injected into a spherical mold with a diameter of 2 mm, kept at 115℃ for 2.5 h, and then heated to 1300℃ at a heating rate of 3℃ / min and kept at 1300℃ for 2.5 h to obtain a ceramic body; wherein, the mass ratio of steel slag, bauxite tailings and fly ash is 42∶53∶76, the average particle size of alumina powder is 500 nm, the amount of water added is 3% of the mass of fly ash, and the amount of ammonium polyacrylate added is 0.2% of the mass of fly ash; other steps are the same as in Example 3.

[0068] Slagging rate refers to the percentage of the mass of ash particles larger than 6 mm that agglomerate after combustion of a biomass fuel sample under a specified blast intensity, relative to the total ash mass. This invention, following the method for determining the slagging properties of biomass solid fuels in NB / T34025-2015, tested the slagging properties of biomass fuels prepared in Examples 1-3 and Comparative Examples 1-3, at an air flow rate of 6 m³ / s. 3 Three repeated measurements were performed at a blower speed of 0.1 m / s, 0.2 m / s, and 0.3 m / s, respectively. The difference between the results of each two repeated measurements should not exceed 5% (absolute value). The average value was then taken. The results are shown in Table 1.

[0069] Table 1

[0070]

[0071] As can be seen from Table 1, the biomass fuel provided by this invention has a low slagging rate, ranging from only 1.93% to 2.89%. Compared with Example 3, Comparative Example 1, due to the omission of porous ceramics, cannot effectively capture and fix components such as alkali metals in the ash, resulting in a significantly higher slagging rate of the obtained biomass fuel; Comparative Example 2, due to the omission of anti-slagging agent, also shows a significantly higher slagging rate of the obtained biomass fuel; Comparative Example 3, due to the change in the composition of porous ceramics and the reduction of the porosity of the porous ceramics, also shows a significantly higher slagging rate of the obtained biomass fuel compared to Example 3.

[0072] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An anti-caking biomass fuel, characterized by, The raw materials include the following components by weight: crop straw 90-120 parts, tree branches 30-50 parts, anti-slagging agent 0.9-6 parts, and porous ceramic 0.2-0.35 parts; The anti-slagging agent includes the following components by weight: magnesium carbonate 15-25%, aluminum oxide 20-30%, and calcium carbonate 45-65%; The raw materials for preparing the porous ceramic include steel slag, bauxite tailings, fly ash, aluminum oxide powder, calcium carbonate, and sodium borate; the mass ratio of the steel slag, bauxite tailings, fly ash, aluminum oxide powder, calcium carbonate, and sodium borate is (30-45):(40-55):(65-85):(15-25):(5-8):(6-12).

2. The anti-caking biomass fuel according to claim 1, characterized by, The crop straw is selected from at least one of corn straw, sorghum straw, and rice straw.

3. The anti-caking biomass fuel according to claim 1, wherein, The tree branches are selected from at least one of peach tree branches, apple tree branches, and pear tree branches.

4. The anti-caking biomass fuel of claim 1, wherein, The raw materials for preparing the porous ceramic further include a dispersing agent; the dispersing agent is selected from sodium polyphosphate, ammonium polyacrylate, or ammonium oxalate; the amount of the dispersing agent is 0.1-0.3% of the mass of the fly ash.

5. The anti-caking biomass fuel according to claim 4, wherein The method for preparing the porous ceramic includes the following steps: uniformly mixing steel slag, bauxite tailings, fly ash, aluminum oxide powder, calcium carbonate, and sodium borate to obtain a mixture; adding water and a dispersing agent to the mixture, uniformly mixing, and then forming and sintering to obtain the porous ceramic.

6. The anti-caking biomass fuel according to claim 5, wherein, The forming temperature is 100-150°C, and the forming time is 2-3h.

7. The anti-caking biomass fuel according to claim 5, wherein The sintering temperature is 1250-1350°C, the sintering holding time is 2-3h, and the heating rate to the sintering temperature is 2-5°C / min.

8. A method of producing an anti-caking biomass fuel according to any one of claims 1 to 7, characterized by, The method includes the following steps: The crop straw and the tree branches are crushed and sieved, and then mixed with the anti-slagging agent and the porous ceramic, and then pressure-formed to obtain the anti-slagging biomass fuel.

9. The method of claim 8, wherein the biomass fuel is prepared by The sieving is through a 1-2mm sieve; and / or The pressure-forming temperature is room temperature, the pressure-forming pressure is 50-80MPa, and the pressure-forming time is 50-100s.

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