A method for producing charcoal fuel from corn stalks based on functional composite binders

Abstract

This invention proposes a method for producing charcoal fuel from corn stalks based on a functional composite binder, belonging to the field of biomass solid fuel preparation technology. The invention involves uniformly mixing corn stalk charcoal powder with a functional composite binder to obtain a mixture, followed by hot pressing and activation molding to obtain corn stalk charcoal fuel. The raw materials of the functional composite binder include phosphoric acid, polysilicic acid, polyethylene, and sodium lignosulfonate; the amount of the functional composite binder added to the corn stalk charcoal powder is 10-15 wt.%. In this method, the controllability of the raw material charcoal quality is significantly improved, and the use of a functional composite binder enhances the molding density, shatter resistance, and durability of the charcoal fuel. Furthermore, the process of this invention exhibits high stability and repeatability, laying the foundation for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of biomass solid fuel preparation technology, and particularly relates to a method for producing charcoal fuel from corn stalks based on a functional composite binder. Background Technology

[0002] As the global energy structure accelerates its transition towards cleaner and lower-carbon energy, biomass energy, as the only renewable energy source capable of sequestering carbon, has become one of the core pathways to resolving the contradiction between the shortage of traditional fossil fuels and environmental pollution. As a major agricultural country, my country generates a large amount of corn stalks every year. However, traditional methods of treating this carbon-rich agricultural waste have significant drawbacks.

[0003] After high-temperature carbonization, corn stalks undergo a qualitative leap in performance: the organic carbon content can be increased to over 42%, the ash content controlled below 8.5%, and the calorific value exceeds 28 MJ / kg, far surpassing that of raw stalks (approximately 15 MJ / kg). Furthermore, a porous structure with an average pore size of 7.45 nm is formed, combining fuel properties with adsorption potential, making it a high-quality solid fuel raw material to replace coal. However, existing technological bottlenecks severely restrict its large-scale application: First, the carbonization process often uses open or simple atmosphere furnaces, where the residual oxygen content often exceeds 1%, leading to uneven carbonization and resulting in localized over-burning (char body embrittlement) or uncarbonized (high oxygen content, low calorific value), with char quality fluctuations reaching over 20%. Second, the molding stage relies on single binders such as sodium lignosulfonate, resulting in a molding density generally below 1.2 g / cm³. 3 The mechanical strength is less than 1.0 MPa, and the breakage rate during transportation and storage exceeds 15%, which greatly increases losses. Third, during fuel combustion, due to the high content of alkali metals (K, Na) in the ash, the slagging rate often exceeds 15%, which not only reduces the boiler thermal efficiency (the reduction can reach 10%-15%), but also requires frequent shutdowns for slagging, increasing operation and maintenance costs. In addition, in most processes, the carbonization and molding stages are disconnected, the production process takes 8-12 hours, and the energy consumption accounts for more than 30%, which further increases product costs and makes it difficult to meet the needs of industrialization.

[0004] Therefore, developing a method for producing charcoal fuel from corn stalks based on functional composite binders is of great practical significance for promoting the efficient utilization of corn stalk resources and assisting in the green and low-carbon transformation of agriculture. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a method for producing charcoal fuel from corn stalks based on a functional composite binder.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for producing charcoal fuel from corn stalks based on a functional composite binder includes the following steps:

[0008] Corn stalk charcoal powder is mixed evenly with a functional composite binder to obtain a mixture, which is then hot-pressed and activated to obtain corn stalk charcoal fuel. The raw materials of the functional composite binder include phosphoric acid, polysilicic acid, polyethylene and sodium lignosulfonate. The amount of the functional composite binder added to the corn stalk charcoal powder is 10-15 wt.

[0009] Furthermore, the mass ratio of phosphoric acid, polysilicic acid, polyethylene and sodium lignosulfonate in the raw materials of the functional composite adhesive is 8:(1-4):3:7.

[0010] Furthermore, the preparation method of the functional composite adhesive includes the following steps:

[0011] Weigh each raw material according to the mass ratio, mix phosphoric acid and polysilicic acid, calcine at 600±20℃ for 4 hours, cool and grind to obtain phosphorus-silica composite powder;

[0012] The phosphorus-silica composite powder, polyethylene and sodium lignosulfonate are mixed, water is added to adjust the solid content to 60%-70%, and the mixture is stirred evenly to obtain the functional composite adhesive.

[0013] In the preparation process of the functional composite binder of this invention, phosphoric acid and polysilicic acid are first mixed and calcined (600±20℃, 4h) to generate phosphorus-silica composite powder. The calcination process causes a condensation reaction between phosphoric acid and polysilicic acid, forming inorganic composite particles with a porous structure. These particles can fill the porous gaps of corn stalk charcoal, reducing the porosity inside the molded body. At the same time, their rigid structure can act as a "skeleton" to support the charcoal particles, preventing structural collapse caused by external pressure after molding. Polyethylene is a thermoplastic resin, and the hot pressing temperature (180-200℃) is exactly within its melting range (polyethylene melting point is about 110-130℃, and the fluidity is best at 180-200℃). After melting, a continuous adhesive film can be formed on the surface of the charcoal particles, tightly wrapping the dispersed charcoal particles and phosphorus-silica composite powder, eliminating interfacial voids between particles. The hot pressing pressure of 100-130MPa further promotes close contact between the particles, increasing the density of the molded body. Sodium lignosulfonate contains a large number of polar groups such as hydroxyl (-OH) and sulfonic acid (-SO3H), which can form hydrogen bonds with the hydroxyl groups on the surface of corn stalk charcoal, and at the same time bind with the non-polar segments of polyethylene through van der Waals forces, achieving a strong multi-interface bond between "inorganic particles-organic binder-charcoal particles". The subsequent activation at 220±10℃ (holding temperature for 1.5h) can promote further cross-linking between the binder and charcoal particles, thereby improving the compressive strength of the molded fuel.

[0014] The phosphorus-silica composite powder in the functional composite binder of this invention contains phosphoric acid derivatives. During combustion, the phosphorus element reacts with alkali metals (K, Na) in the ash of corn stalk char to form stable phosphates. These phosphates have melting points much higher than the combustion temperature of charcoal fuel, preventing the alkali metals from melting and forming a sticky melt, thus reducing boiler slag removal frequency and improving thermal efficiency. Silica disperses ash, preventing agglomeration. The silica in the phosphorus-silica composite powder is an inert inorganic particle that acts as a "dispersant" during combustion, uniformly distributing in the ash and preventing ash particles from agglomerating, further inhibiting slag formation. Simultaneously, its porous structure can adsorb some small molecule pollutants (such as SO2) generated during combustion, reducing harmful gas emissions.

[0015] Furthermore, the hot pressing activation molding involves placing the mixture into a mold preheated to 180-200°C, holding it under pressure of 100-130 MPa for 2 minutes, and then, under a protective atmosphere, raising the temperature to 220±10°C at a rate of 5°C / min and holding it at that temperature for 1.5 hours.

[0016] Furthermore, the corn stalk charcoal powder is prepared by pre-treating and carbonizing corn stalk waste.

[0017] Furthermore, the pretreatment step is as follows: the corn stalk waste is dried at 75±5℃ for 12-16h, then crushed to a particle size ≤0.16mm, and then dried at 105±2℃ to constant weight.

[0018] The low-temperature drying process in this invention removes over 80% of the free water and some bound water from the straw, preventing clumping during subsequent crushing. Drying to constant weight ensures that the moisture content of each batch of pretreated straw is ≤2%, completely eliminating variations in carbonization levels caused by differences in raw material moisture content and laying the foundation for stable carbonization. Simultaneously, crushing to a particle size ≤0.16mm ensures uniform straw particle surface area, resulting in consistent heat transfer during carbonization and preventing localized uncarbonized areas.

[0019] Furthermore, the carbonization step is as follows: the pretreated straw is heated to 500±10℃ at a heating rate of 5-10℃ / min under a protective atmosphere and kept at that temperature for 4 hours.

[0020] In the carbonization process of this invention, the protective atmosphere isolates oxygen, ensuring that the residual oxygen content in the furnace is ≤0.5%, thus preventing excessive oxidation or localized combustion of the straw during carbonization (resulting in pores and embrittlement of the charcoal body). The slow heating rate of 5-10℃ / min allows the cellulose, hemicellulose, and lignin in the straw to decompose gradually (hemicellulose decomposes at 200-300℃, cellulose at 300-400℃, and lignin at 250-500℃), generating a stable graphite-like carbon structure. Holding at 500±10℃ for 4 hours ensures that the organic carbon is fully retained (organic carbon content ≥42%), and the ash content (mainly inorganic minerals) is effectively fixed and ≤8.5%, ultimately yielding corn straw charcoal powder raw material with high carbon content and good quality.

[0021] Furthermore, the amount of the functional composite binder added to the corn straw charcoal powder is 12 wt.%.

[0022] A corn stalk charcoal fuel prepared according to the above method.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] (1) The method of the present invention significantly improves the controllability of raw material char quality. Existing technologies often result in char body embrittlement or high oxygen content due to high residual oxygen and uneven heating during carbonization. The present invention eliminates the difference in raw material moisture by "pre-drying at 75±5℃ + constant weight at 105±2℃", and solves the problem of quality fluctuation of traditional char by combining nitrogen-protected carbonization (oxygen residue ≤0.5%) and precise heating at 5-10℃ / min.

[0025] (2) Existing technologies rely on a single binder, resulting in low molding density and insufficient resistance to breakage. The functional composite binder of this invention (phosphorus-silica-polyethylene-sodium lignosulfonate) forms an inorganic skeleton through calcination, melts polyethylene to form a film, and bonds polar groups, achieving a molding density as high as 1.12 g / cm³. 3 It has a drop and breakage resistance of 95.3%, a durability of 83.6%, and a breakage rate of less than 5% during transportation.

[0026] (3) The functional composite binder used in this invention can utilize phosphorus-silicon synergy to inhibit alkali metal melting, resulting in a slagging rate as low as 1.48% (weak slagging level); and the fuel's S and N content is only 0.11-0.13% and 0.34-0.37%, respectively, with combustion pollutant emissions far below the standards. At the same time, straw resource utilization replaces burning, reducing CO2 emissions, thus achieving both high efficiency and environmental protection. Furthermore, the process of this invention is stable and highly repeatable, laying the foundation for large-scale production. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] This invention provides a method for producing charcoal fuel from corn stalks based on a functional composite binder, comprising the following steps:

[0033] Corn stalk charcoal powder is uniformly mixed with a functional composite binder to obtain a mixture, which is then hot-pressed and activated to form corn stalk charcoal fuel. The raw materials of the functional composite binder include phosphoric acid, polysilicic acid, polyethylene, and sodium lignosulfonate. The amount of the functional composite binder added to the corn stalk charcoal powder is 10-15 wt.%. The specific steps include:

[0034] (1) Preparation of corn stalk charcoal powder

[0035] a. Pretreatment: After removing impurities from the corn stalk waste, dry it in an oven at 75±5℃ for 12-16 hours, then crush it with a pulverizer to a particle size ≤0.16mm, and then dry it in an electric heating blast drying oven at 105±2℃ until constant weight.

[0036] b. Atmosphere-protected carbonization: The pretreated straw powder is loaded into a crucible and placed in a tube furnace. Nitrogen gas with a purity of ≥99.99% is introduced to purge oxygen for 20-30 minutes. The temperature is raised to 500±10℃ at a rate of 5-10℃ / min and held for 4 hours. After the holding period, nitrogen gas is continued to be introduced to cool naturally to room temperature. The powder is then removed, sealed, and stored to obtain corn straw charcoal powder.

[0037] (2) Preparation of functional composite adhesives

[0038] Phosphoric acid and polysilicic acid were mixed at a mass ratio of 8:(1-4), and the pH was adjusted to 3.5±0.2 with 29wt.% ammonium hydroxide solution. The mixture was then calcined in a muffle furnace at 600±20℃ for 4 hours. After cooling, the mixture was ground to a particle size ≤3μm to obtain phosphorus-silica composite powder. The obtained phosphorus-silica composite powder was mixed with polyethylene and lignin sulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignin sulfonate was 8:3:7. Deionized water was then added to adjust the solid content to 60%-70%, and the mixture was stirred at 300-500r / min for 30min to obtain a functional composite binder.

[0039] (3) Preparation of the mixture

[0040] Mix the corn stalk charcoal powder obtained in step (1) with the functional composite binder obtained in step (2). The amount of functional composite binder added to the corn stalk charcoal powder is 10-15 wt.%. Grind the mixture in a ball mill for 15-20 min to ensure uniform mixing.

[0041] (4) Hot pressing activation molding

[0042] The mixture obtained in step (3) is placed in a mold preheated to 180-200℃ and held under pressure of 100-130MPa for 2 minutes. Then, the hot-pressed block is placed back into the tube furnace and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 220±10℃ at a rate of 5℃ / min and held for 1.5 hours. Then, nitrogen gas is introduced to cool it to room temperature to obtain corn straw charcoal fuel. The finished product is sealed and stored in a moisture-proof container.

[0043] In this embodiment of the invention, room temperature refers to "25±2℃".

[0044] The technical solution of the present invention will be further illustrated by the following embodiments.

[0045] Example 1

[0046] A method for producing charcoal fuel from corn stalks based on a functional composite binder, specifically including the following steps:

[0047] (1) Preparation of corn stalk charcoal powder

[0048] a. Pretreatment: After removing impurities from the corn stalk waste, dry it in an oven at 75±5℃ for 14 hours, then crush it with a pulverizer to a particle size ≤0.16mm, and then dry it in an electric heating blast drying oven at 105±2℃ until constant weight.

[0049] b. Atmosphere-protected carbonization: The pretreated straw powder is loaded into a crucible and placed in a tube furnace. Nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 500±10℃ at a rate of 8℃ / min and held for 4 hours. After the holding period, nitrogen gas is introduced to cool naturally to room temperature. The powder is then removed, sealed, and stored to obtain corn straw charcoal powder.

[0050] (2) Preparation of functional composite adhesives

[0051] Phosphoric acid and polysilicic acid were mixed at a mass ratio of 8:3, and the pH was adjusted to 3.5±0.2 with 29wt.% ammonium hydroxide solution (ammonia water). The mixture was then calcined in a muffle furnace at 600±20℃ for 4 hours. After cooling, the mixture was ground to a particle size ≤3μm to obtain phosphorus-silica composite powder. The obtained phosphorus-silica composite powder was mixed with polyethylene and lignin sulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignin sulfonate was 8:3:7. Deionized water was then added to adjust the solid content to 60%, and the mixture was stirred at 400r / min for 30min to obtain a functional composite binder.

[0052] (3) Preparation of the mixture

[0053] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2). The amount of functional composite binder added to the corn stalk charcoal powder is 12 wt.%, and the mixture is ground in a ball mill for 18 min to ensure uniform mixing.

[0054] (4) Hot pressing activation molding

[0055] The mixture obtained in step (3) is placed in a mold preheated to 185°C and held under pressure of 120MPa for 2 minutes. Then, the hot-pressed block is placed back into the tube furnace and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 220±10°C at a rate of 5°C / min and held for 1.5 hours. Then, nitrogen gas is introduced to cool it to room temperature to obtain corn straw charcoal fuel. The finished product is sealed and stored in a moisture-proof container.

[0056] Example 2

[0057] A method for producing charcoal fuel from corn stalks based on a functional composite binder, specifically including the following steps:

[0058] (1) Preparation of corn stalk charcoal powder

[0059] a. Pretreatment: After removing impurities from the corn stalk waste, dry it in an oven at 75±5℃ for 16 hours, then crush it with a pulverizer to a particle size ≤0.16mm, and then dry it in an electric heating forced-air drying oven at 105±2℃ until constant weight.

[0060] b. Atmosphere-protected carbonization: The pretreated straw powder is loaded into a crucible and placed in a tube furnace. Nitrogen gas with a purity of ≥99.99% is introduced to purge oxygen for 30 minutes. The temperature is raised to 500±10℃ at a rate of 5℃ / min and held for 4 hours. After the holding period, nitrogen gas is continued to be introduced to cool naturally to room temperature. The powder is then removed, sealed, and stored to obtain corn straw charcoal powder.

[0061] (2) Preparation of functional composite adhesives

[0062] Phosphoric acid and polysilicic acid were mixed at a mass ratio of 8:1, and the pH was adjusted to 3.5±0.2 with 29wt.% ammonium hydroxide solution. The mixture was then calcined in a muffle furnace at 600±20℃ for 4 hours. After cooling, the mixture was ground to a particle size ≤3μm to obtain phosphorus-silica composite powder. The obtained phosphorus-silica composite powder was mixed with polyethylene and lignin sulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignin sulfonate was 8:3:7. Deionized water was then added to adjust the solid content to 70%, and the mixture was stirred at 500r / min for 30min to obtain a functional composite binder.

[0063] (3) Preparation of the mixture

[0064] Mix the corn stalk charcoal powder obtained in step (1) with the functional composite binder obtained in step (2). The amount of functional composite binder added to the corn stalk charcoal powder is 15 wt.%. Grind the mixture in a ball mill for 15 min to ensure uniform mixing.

[0065] (4) Hot pressing activation molding

[0066] The mixture obtained in step (3) is placed in a mold preheated to 180°C and held under pressure of 130MPa for 2 minutes. Then, the hot-pressed block is placed back into the tube furnace and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 220±10°C at a rate of 5°C / min and held for 1.5 hours. Then, nitrogen gas is introduced to cool it to room temperature to obtain corn straw charcoal fuel. The finished product is sealed and stored in a moisture-proof container.

[0067] Example 3

[0068] A method for producing charcoal fuel from corn stalks based on a functional composite binder, specifically including the following steps:

[0069] (1) Preparation of corn stalk charcoal powder

[0070] a. Pretreatment: After removing impurities from the corn stalk waste, dry it in an oven at 75±5℃ for 12 hours, then crush it with a pulverizer to a particle size ≤0.16mm, and then dry it in an electric heating blast drying oven at 105±2℃ until constant weight.

[0071] b. Atmosphere-protected carbonization: The pretreated straw powder is loaded into a crucible and placed in a tube furnace. Nitrogen gas with a purity of ≥99.99% is introduced to purge oxygen for 20-30 minutes. The temperature is raised to 500±10℃ at a rate of 10℃ / min and held for 4 hours. After the holding period, nitrogen gas is continued to be introduced to cool naturally to room temperature. The powder is then removed, sealed, and stored to obtain corn straw charcoal powder.

[0072] (2) Preparation of functional composite adhesives

[0073] Phosphoric acid and polysilicic acid were mixed at a mass ratio of 8:4, and the pH was adjusted to 3.5±0.2 with 29wt.% ammonium hydroxide solution. The mixture was then calcined in a muffle furnace at 600±20℃ for 4 hours. After cooling, the mixture was ground to a particle size ≤3μm to obtain phosphorus-silica composite powder. The obtained phosphorus-silica composite powder was mixed with polyethylene and lignin sulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignin sulfonate was 8:3:7. Deionized water was then added to adjust the solid content to 60%, and the mixture was stirred at 300r / min for 30min to obtain a functional composite binder.

[0074] (3) Preparation of the mixture

[0075] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2). The amount of functional composite binder added to the corn stalk charcoal powder is 10 wt.%. The mixture is ground in a ball mill for 20 min to ensure uniform mixing.

[0076] (4) Hot pressing activation molding

[0077] The mixture obtained in step (3) is placed in a mold preheated to 200°C and held under pressure of 100MPa for 2 minutes. Then, the hot-pressed block is placed back into the tube furnace and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 220±10°C at a rate of 5°C / min and held for 1.5 hours. Then, nitrogen gas is introduced to cool it to room temperature to obtain corn straw charcoal fuel. The finished product is sealed and stored in a moisture-proof container.

[0078] Example 4

[0079] A method for producing charcoal fuel from corn stalks based on a functional composite binder, specifically including the following steps:

[0080] (1) Preparation of corn stalk charcoal powder

[0081] a. Pretreatment: After removing impurities from the corn stalk waste, dry it in an oven at 75±5℃ for 13 hours, then crush it with a pulverizer to a particle size ≤0.16mm, and then dry it in an electric heating blast drying oven at 105±2℃ until constant weight.

[0082] b. Atmosphere-protected carbonization: The pretreated straw powder is loaded into a crucible and placed in a tube furnace. Nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 30 minutes. The temperature is raised to 500±10℃ at a rate of 6℃ / min and held for 4 hours. After the holding period, nitrogen gas is introduced to cool naturally to room temperature. The powder is then removed, sealed, and stored to obtain corn straw charcoal powder.

[0083] (2) Preparation of functional composite adhesives

[0084] Phosphoric acid and polysilicic acid were mixed at a mass ratio of 8:3, and the pH was adjusted to 3.5±0.2 with 29wt.% ammonium hydroxide solution. The mixture was then calcined in a muffle furnace at 600±20℃ for 4 hours. After cooling, the mixture was ground to a particle size ≤3μm to obtain phosphorus-silica composite powder. The obtained phosphorus-silica composite powder was mixed with polyethylene and lignin sulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignin sulfonate was 8:3:7. Deionized water was then added to adjust the solid content to 66%, and the mixture was stirred at 380r / min for 30min to obtain a functional composite binder.

[0085] (3) Preparation of the mixture

[0086] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2). The amount of functional composite binder added to the corn stalk charcoal powder is 13 wt.%. The mixture is ground in a ball mill for 18 min to ensure uniform mixing.

[0087] (4) Hot pressing activation molding

[0088] The mixture obtained in step (3) is placed in a mold preheated to 190°C and held under pressure of 110MPa for 2 minutes. Then, the hot-pressed block is placed back into the tube furnace and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 220±10°C at a rate of 5°C / min and held for 1.5 hours. Then, nitrogen gas is introduced to cool it to room temperature to obtain corn straw charcoal fuel. The finished product is sealed and stored in a moisture-proof container.

[0089] Comparative Example 1

[0090] Same as Example 1, except that step (2) is different, specifically:

[0091] Phosphoric acid, polysilicic acid, polyethylene and sodium lignosulfonate were mixed in a mass ratio of 8:3:3:7, then deionized water was added to adjust the solid content to 60%, and the mixture was stirred at 400 r / min for 30 min to obtain a functional composite adhesive.

[0092] Comparative Example 2

[0093] Same as Example 1, except that step (2) is different, specifically:

[0094] Phosphoric acid was adjusted to pH 3.5 ± 0.2 with 29 wt.% ammonium hydroxide solution, then calcined in a muffle furnace at 600 ± 20℃ for 4 h. After cooling, it was ground to a particle size ≤ 3 μm to obtain a composite powder. The obtained composite powder was mixed with polyethylene and lignin sulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignin sulfonate was 8:3:7. Then, deionized water was added to adjust the solid content to 60%, and the mixture was stirred at 400 r / min for 30 min to obtain a functional composite binder.

[0095] Comparative Example 3

[0096] Same as Example 1, except that step (1) is different, specifically:

[0097] After removing impurities from the corn stalk waste, it was dried in an oven at 75±5℃ for 14 hours, then pulverized with a pulverizer to a particle size ≤0.16mm, and then dried in an electric heating forced-air drying oven at 105±2℃ until constant weight, to obtain corn stalk powder.

[0098] Comparative Example 4

[0099] Same as Example 1, except that step (4) is different, specifically:

[0100] The mixture obtained in step (3) is placed in a mold preheated to 100°C and held under pressure of 80MPa for 2 minutes. Then, the hot-pressed block is placed back into the tube furnace and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 minutes. The temperature is raised to 220±10°C at a rate of 5°C / min and held for 1.5 hours. Then, nitrogen gas is introduced to cool it to room temperature to obtain corn straw charcoal fuel. The finished product is sealed and stored in a moisture-proof container.

[0101] Performance testing

[0102] Test subjects: Corn straw charcoal fuels prepared in Examples 1-4 and Comparative Examples 1-4.

[0103] Molding performance: Density was determined according to GB / T25211-2010 "Test Methods for Biomass Solid Molded Fuel"; Drop resistance was determined according to GB / T25211-2010, after three free drops from a height of 1.5m, the mass percentage of particles with a diameter >3mm was weighed; Durability was determined according to GB / T18856.1-2019 "Test Methods for Coal-Water Slurry Part 1: Sampling", after a drum test, the percentage of unbroken particles was weighed.

[0104] Combustion performance: Ignition temperature and burnout temperature were determined by thermogravimetric analysis (heating rate 10℃ / min, air atmosphere); calorific value was determined by oxygen bomb calorimeter according to GB / T30727-2014 "Determination of calorific value of solid biomass fuels".

[0105] Environmental performance: The slagging rate was determined according to GB / T1574-2007 "Methods for Analysis of Coal Ash Components", and the mass percentage of molten slag was measured after combustion under a blower intensity of 0.2 m / s; the sulfur (S) and nitrogen (N) contents were determined by an elemental analyzer according to GB / T28732-2012 "Methods for Determination of Total Sulfur in Solid Biomass Fuels".

[0106] The performance test results are shown in Table 1.

[0107] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-4

[0108]

[0109] As shown in Table 1, Example 1 exhibits the highest molding density, shatter resistance, and durability; the phosphorus-silicon synergy is fully realized, resulting in a slagging rate as low as 1.48%, and the high-carbon carbon powder ensures a calorific value of 19150 kJ·kg⁻¹. -1 Examples 2-4 all meet the usage requirements. Reasons for the performance degradation in the comparative examples:

[0110] Comparative Example 1 (Binder not calcined): Without calcination to form phosphorus-silica composite powder, the bonding force between the binder and carbon powder was weak, resulting in a molding density reduced to 0.98 g / cm³. 3 Its drop resistance and durability are only 82.5% and 70.1%, respectively.

[0111] Comparative Example 2 (Polysilicic Acid Deficiency): Without the participation of polysilicic acid, there is no phosphorus-silicon synergistic effect in reducing slagging, the slagging rate soars to 3.26%, and the support of the molded skeleton is insufficient, with a drop resistance of only 85.3%;

[0112] Comparative Example 3 (Uncarbonized): Direct molding with dried straw powder failed to form a high-carbon structure, and the calorific value dropped sharply to 10230 kJ·kg. -1 Furthermore, the raw materials contained many impurities, resulting in a slagging rate of 8.75% and a comprehensive deterioration in molding performance.

[0113] Comparative Example 4 (low hot-pressing parameters): The hot-pressing temperature of 100℃ did not reach the melting range of polyethylene, and the pressure of 80MPa was insufficient, resulting in poor compactness of the molded body with a density of 0.95g / cm³. 3 Its drop and breakage resistance is only 78.6%, and uneven oxygen penetration during combustion causes the burnout temperature to rise to 530.1℃.

[0114] 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. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing charcoal fuel from corn stalks based on a functional composite binder, characterized in that, Includes the following steps: Corn stalk charcoal powder is uniformly mixed with a functional composite binder to obtain a mixture, which is then hot-pressed and activated to form corn stalk charcoal fuel. The raw materials of the functional composite binder include phosphoric acid, polysilicic acid, polyethylene, and sodium lignosulfonate. The amount of the functional composite binder added to the corn stalk charcoal powder is 10-15 wt.%. The preparation method of the functional composite adhesive includes the following steps: Weigh each raw material according to the mass ratio, mix phosphoric acid and polysilicic acid, calcine, cool and grind to obtain phosphorus-silica composite powder; The phosphorus-silica composite powder, polyethylene and sodium lignosulfonate are mixed, water is added to adjust the solid content, and the mixture is stirred evenly to obtain the functional composite adhesive. The corn stalk charcoal powder is prepared by pre-treating and carbonizing corn stalk waste. The pre-treatment steps are as follows: drying the corn stalk waste at 75±5℃ for 12-16h, then crushing it to a particle size ≤0.16mm, and then drying it at 105±2℃ to a constant weight. The hot-press activation molding process involves placing the mixture into a mold preheated to 180-200℃, holding it under pressure of 100-130MPa for 2 minutes, and then heating it to 220±10℃ at a rate of 5℃ / min under a protective atmosphere and holding it at that temperature for 1.5 hours.

2. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 1, characterized in that, The mass ratio of phosphoric acid, polysilicic acid, polyethylene and sodium lignosulfonate in the raw materials of the functional composite adhesive is 8:(1-4):3:

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3. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 1, characterized in that, The calcination was carried out at 600±20℃ for 4 hours, and water was added to adjust the solid content to 60%-70%.

4. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 1, characterized in that, The carbonization step is as follows: the pretreated straw is heated to 500±10℃ at a heating rate of 5-10℃ / min under a protective atmosphere and kept at that temperature for 4 hours.

5. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 1, characterized in that, The amount of the functional composite binder added to the corn straw charcoal powder is 12 wt.%.

6. A corn stalk charcoal fuel prepared by the method according to any one of claims 1-5.

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