Method for preparing carbon fuel from corn straw based on functional composite binder

Abstract

The invention provides a method for preparing carbon fuel from corn straw based on a functional composite binder, and belongs to the technical field of biomass solid fuel preparation. The preparation method comprises the following steps: uniformly mixing corn stalk charcoal powder with a functional composite binder to obtain a mixture, and then carrying out hot-pressing activation molding to obtain the corn stalk charcoal fuel. The functional composite binder comprises the following raw materials: phosphoric acid, polysilicic acid, polyethylene and sodium lignin sulfonate; the addition amount of the functional composite binder in the corn stalk carbon powder is 10-15 wt.%. According to the method, the controllability of the quality of the raw material carbon is greatly improved, the functional composite binder is adopted, the forming density, falling and breaking resistance and durability of the carbon fuel are improved, the process stability and repeatability are high, and a foundation is laid for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biomass solid fuel preparation, and particularly relates to a method for preparing corn straw charcoal fuel based on a functional composite binder. BACKGROUND

[0002] With the acceleration of the transformation of global energy structure towards clean and low-carbon, biomass energy, as the only renewable energy that can fix carbon, has become one of the core paths to break the contradiction between traditional fossil energy shortage and environmental pollution. As a large agricultural country, China produces a large amount of corn straw every year. The traditional treatment method of this kind of agricultural waste rich in carbon resources has significant drawbacks. Open burning not only releases a large amount of PM2.5, SO2 and other pollutants (a single large-scale burning can make the regional PM2.5 concentration rise by 3-5 times), causing environmental problems such as haze and acid rain, but also causes direct waste of carbon resources. Simple composting not only has a degradation period of 3-6 months, but also easily causes soil nitrogen and phosphorus loss due to microbial imbalance during the process, which not only cannot efficiently recover energy, but also aggravates the ecological pressure on farmland.

[0003] After high-temperature carbonization treatment, the performance of corn straw is qualitatively improved: the organic carbon content can be increased to more than 42%, the ash content is controlled to be less than 8.5%, the heat value breaks through 28 MJ / kg, which is much higher than that of original straw (about 15 MJ / kg), and a porous structure with an average pore size of 7.45 nm is formed, which has both fuel properties and adsorption potential, and is a high-quality solid fuel raw material to replace coal. However, the existing technical bottlenecks seriously restrict its large-scale application: first, the carbonization process mostly uses open or simple atmosphere furnaces, and the residual oxygen content in the furnace is often more than 1%, which leads to uneven carbonization and local overburning (carbon body brittleness) or non-carbonization (high oxygen content and low heat value), and the carbon quality fluctuation range can reach more than 20%; second, the forming stage relies on a single sodium lignosulfonate binder, and the forming density is generally less than 1.2 g / cm3, the mechanical strength is less than 1.0 MPa, and the fragmentation rate during transportation and storage is more than 15%, which greatly increases the loss; third, due to the high content of alkali metals (K, Na) in the ash, the slagging rate often breaks through 15%, which not only reduces the boiler thermal efficiency (the reduction can reach 10%-15%), but also needs to frequently stop the furnace for slag removal, increasing the operation and maintenance cost; in addition, the carbonization and forming links are disconnected in most processes, and the production process is as long as 8-12 hours, and the energy consumption accounts for more than 30%, which further increases the product cost and makes it difficult to meet the industrialization demand. 3

[0004] Therefore, it is of important practical significance to develop a method for preparing corn straw charcoal fuel based on a functional composite binder to promote the efficient utilization of corn straw resources and help the green and low-carbon transformation of agriculture. SUMMARY

[0005] ​To solve the above technical problems, the present application provides a method for making corn stalk charcoal fuel based on functional composite binder.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] A method for making corn stalk charcoal fuel based on functional composite binder, comprising the following steps:

[0008] Mixing corn stalk charcoal powder with functional composite binder to obtain a mixture, and then hot-pressing and activating to form corn stalk charcoal fuel; the raw materials of the functional composite binder include phosphoric acid, polysilicic acid, polyethylene and sodium lignosulfonate; the addition amount of the functional composite binder in the corn stalk charcoal powder is 10-15 wt.%.

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

[0010] Still further, the preparation method of the functional composite binder comprises the following steps:

[0011] Taking each raw material according to the mass ratio, mixing phosphoric acid with polysilicic acid, calcining at 600±20℃ for 4h, grinding after cooling to obtain phosphorus-silicon dioxide composite powder;

[0012] Mixing the phosphorus-silicon dioxide composite powder, polyethylene and sodium lignosulfonate, adding water to adjust the solid content to 60%-70%, and stirring uniformly to obtain the functional composite binder.

[0013] In the preparation process of the functional composite binder, phosphoric acid and polysilicic acid are first mixed and calcined (600±20℃, 4h) to generate phosphorus-silicon dioxide composite powder. The calcination process causes the condensation reaction of phosphoric acid and polysilicic acid to form inorganic composite particles with a porous structure. The particles can fill the porous gaps of corn stalk charcoal, reduce the internal porosity of the formed body, and at the same time, the rigid structure can serve as a "skeleton" to support the charcoal particles, avoiding the collapse of the structure caused by external pressure after forming. Polyethylene is a thermoplastic resin, and the hot-pressing forming temperature (180-200℃) is just in its melting range (the melting point of polyethylene is about 110-130℃, and the fluidity is best at 180-200℃). After melting, a continuous bonding film can be formed on the surface of the charcoal particles, tightly wrapping the dispersed charcoal particles and phosphorus-silicon dioxide composite powder, and eliminating the interfacial voids between the particles. The hot-pressing pressure of 100-130MPa further promotes the close contact of the particles, increasing the density of the formed body. The 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 the corn stalk charcoal, and at the same time, combine with the non-polar segments of polyethylene through van der Waals force, realizing the strong combination of "inorganic particles-organic binder-charcoal particles" at multiple interfaces. Subsequent activation at 220±10℃ (1.5h) can promote the further crosslinking of the binder and the charcoal particles, improving the compressive strength of the formed fuel.

[0014] The phosphorus-silicon dioxide composite powder in the functional composite binder contains phosphorus elements that can react with alkali metals (K, Na) in the ash of corn stalk charcoal to form stable phosphates when the phosphoric acid derivative burns. The melting point of the phosphates is much higher than the combustion temperature of carbon fuel, which can avoid the formation of viscous melt by melting of alkali metals, thereby reducing the frequency of boiler slag removal and improving thermal efficiency. The silicon dioxide disperses the ash to prevent caking. The silicon dioxide in the phosphorus-silicon dioxide composite powder is an inert inorganic particle that can act as a "dispersant" to uniformly distribute in the ash during combustion, preventing the agglomeration of ash particles and further inhibiting slagging. At the same time, its porous structure can adsorb part of the small molecular pollutants (such as SO2) generated during combustion, reducing harmful gas emissions.

[0015] Further, the hot-pressing and activation forming is to put the mixed material into a mold preheated to 180-200℃, and press at a pressure of 100-130MPa for 2min, then in a protective atmosphere, the temperature is raised to 220±10℃ at a rate of 5℃ / min, and the temperature is kept for 1.5h.

[0016] Further, the corn stalk charcoal powder is prepared by pretreating and carbonizing corn stalk waste.

[0017] Further, the pretreatment step is to dry the corn stalk waste at 75±5℃ for 12-16h, then crush it to a particle size of ≤0.16mm, and then dry it to a constant weight at 105±2℃.

[0018] The low-temperature drying of the pretreatment process of the present application can remove more than 80% of free water and part of bound water in the straw, avoiding clumping of the raw material during subsequent crushing; drying to constant weight can ensure that the moisture content of the pretreated straw in each batch is ≤2%, completely eliminating the problem of different carbonization degrees caused by differences in the moisture content of the raw material, and laying a foundation for subsequent stable carbonization. At the same time, crushing to a particle size of ≤0.16 mm makes the specific surface area of the straw particles uniform, and the heat transfer is consistent during carbonization, avoiding local non-carbonization.

[0019] Further, the step of carbonization is: raising the temperature of the pretreated straw to 500±10℃ at a rate of 5-10℃ / min in a protective atmosphere, and keeping it for 4h.

[0020] In the carbonization process of the present application, the protective atmosphere can isolate oxygen, so that the residual oxygen in the furnace is ≤0.5%, avoiding excessive oxidation or local combustion of the straw during carbonization (appearance of holes in the carbon body, embrittlement); the slow heating rate of 5-10℃ / min can gradually decompose cellulose, hemicellulose and lignin in the straw (hemicellulose decomposes at 200-300℃, cellulose decomposes at 300-400℃, and lignin decomposes at 250-500℃), generating a stable graphite-like carbon structure; keeping it at 500±10℃ for 4h ensures that organic carbon is fully retained (organic carbon content ≥42%), and ash (mainly inorganic minerals) is effectively fixed and the content is ≤8.5%, finally obtaining a corn straw carbon powder raw material with high carbon content and good quality.

[0021] Further, the functional composite binder is added to the corn straw carbon powder in an amount of 12wt.%.

[0022] A corn straw carbon fuel prepared according to the above method.

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

[0024] (1) In the method of the present application, the controllability of the quality of the raw material carbon is greatly improved. The prior art often causes carbon body embrittlement or high oxygen content due to excessive residual oxygen during carbonization and uneven heating. The present application eliminates the difference in the moisture content of the raw material by "75±5℃ pre-drying + 105±2℃ constant weight", and solves the problem of quality fluctuation of traditional carbon by combining nitrogen protection carbonization (oxygen residual ≤0.5%) and precise heating at a rate of 5-10℃ / min.

[0025] (2) The prior art relies on a single binder, and the formed density is low and the anti-breaking property is insufficient. The functional composite binder (phosphorus-silicon dioxide-polyethylene-sodium lignosulfonate) of the present application forms an inorganic skeleton by calcination, polyethylene melts into a film, and the polar groups are bonded, and the formed density is as high as 1.12g / cm 3The anti-shattering property is 95.3%, the durability is 83.6%, and the transportation shattering rate is reduced to below 5%.

[0026] (3) The functional composite binder used in the application can inhibit the melting of alkali metals by phosphorus-silicon synergy, and the slagging rate is as low as 1.48% (weak slagging level); and the fuel S and N contents are only 0.11-0.13% and 0.34-0.37%, respectively, and the combustion pollutant emission is far lower than the standard, while the straw resource is replaced by incineration, and the CO2 emission is reduced, and the efficiency and environmental protection are considered. Moreover, the process stability and repeatability of the application lay a foundation for large-scale production. DETAILED DESCRIPTION

[0027] The various exemplary embodiments of the present application will now be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0028] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value within the stated range and any other stated value or intermediate value within the stated range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are concerned. In the event of any conflict between the content of this specification and any document incorporated by reference, the content of this specification will control.

[0030] Various modifications and changes can be made to the specific embodiments of the present application described in this specification without departing from the scope or spirit of the application, which will be apparent to one of ordinary skill in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0031] As used herein, "comprise", "comprising", "have", "having", "include", "including", "contain", "containing", and the like, are open-ended terms that are intended to mean including, but not limited to.

[0032] The present application embodiment proposes a method for making corn stalk charcoal fuel based on a functional composite binder, comprising the following steps:

[0033] The corn straw charcoal powder is mixed with the functional composite binder to obtain a mixture, and then hot-pressed and activated to form a corn straw charcoal fuel; the raw materials of the functional composite binder include phosphoric acid, polysilicic acid, polyethylene and sodium lignosulfonate; the addition amount of the functional composite binder in the corn straw charcoal powder is 10-15 wt.%. It specifically comprises the following steps:

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

[0035] a. Pretreatment: after removing impurities from corn straw waste, drying in an oven at 75±5℃ for 12-16h, then crushing to a particle size of ≤0.16mm with a crusher, and then drying to constant weight in an electric heat air drying oven at 105±2℃;

[0036] b. Atmosphere protection carbonization: the pretreated straw powder is loaded into a crucible and placed in a tube furnace, and pure nitrogen with a purity of ≥99.99% is introduced to remove oxygen for 20-30min, and the temperature is raised to 500±10℃ at a rate of 5-10℃ / min, and the temperature is kept for 4h; after the end of the holding period, continue to pass nitrogen to cool to room temperature, take out and seal, to obtain corn straw charcoal powder;

[0037] (2) Preparation of functional composite binder

[0038] Phosphoric acid and polysilicic acid are mixed in a mass ratio of 8:(1-4), and a 29wt.% ammonium hydroxide solution is used to adjust the pH to 3.5±0.2, and then calcined in a muffle furnace at 600±20℃ for 4h, and then ground to a particle size of ≤3μm after cooling, to obtain a phosphorus-silicon dioxide composite powder; the obtained phosphorus-silicon dioxide composite powder is mixed with polyethylene and sodium lignosulfonate, wherein the mass ratio of phosphoric acid, polyethylene and sodium lignosulfonate is 8:3:7, and then deionized water is added to adjust the solid content to 60%-70%, and stirred at 300-500r / min for 30min, to obtain a functional composite binder;

[0039] (3) Preparation of mixture

[0040] The corn straw charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2), and the addition amount of the functional composite binder in the corn straw charcoal powder is 10-15 wt.%, and the mixture is ground with a ball mill for 15-20min to ensure uniform mixing;

[0041] (4) Hot-pressing and activation molding

[0042] Put the mixture obtained in step (3) into a mold preheated to 180-200℃, and keep pressure for 2 min under a pressure of 100-130 MPa, then put the hot-pressing block into a tube furnace, and oxygen is removed by passing nitrogen gas with a purity of ≥99.99% for 15 min, and the temperature is raised to 220±10℃ at a rate of 5℃ / min, and the temperature is kept for 1.5 h, then nitrogen gas is passed to cool to room temperature, and corn straw charcoal fuel is obtained; the finished product is sealed and moisture-proof stored.

[0043] The room temperature in the embodiment of the application refers to "25±2℃".

[0044] The technical solutions of the application are further described below through examples.

[0045] Example 1

[0046] A method for making corn straw charcoal fuel based on a functional composite binder, specifically comprising the following steps:

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

[0048] a. Pretreatment: after removing impurities from corn straw waste, dry it in an oven at 75±5℃ for 14 h, then crush it to a particle size of ≤0.16 mm with a crusher, and then dry it to a constant weight in an electric heat air drying oven at 105±2℃;

[0049] b. Atmosphere-protected carbonization: put the pretreated straw powder into a crucible and put it into a tube furnace, pass nitrogen gas with a purity of ≥99.99% to remove oxygen for 15 min, and raise the temperature to 500±10℃ at a rate of 8℃ / min, and keep the temperature for 4 h; after the temperature keeping is completed, continue to pass nitrogen gas to cool to room temperature naturally, take out and seal for storage, and obtain corn straw charcoal powder;

[0050] (2) Preparation of functional composite binder

[0051] Mix phosphoric acid and polysilicic acid at a mass ratio of 8:3, adjust the pH to 3.5±0.2 with a 29wt.% ammonium hydroxide solution (ammonia water), then calcine in a muffle furnace at 600±20℃ for 4 h, grind to a particle size of ≤3μm after cooling, and obtain phosphorus-silicon dioxide composite powder; mix the obtained phosphorus-silicon dioxide composite powder with polyethylene and lignosulfonic acid, wherein the mass ratio of phosphoric acid, polyethylene and lignosulfonic acid sodium is 8:3:7, then add deionized water to adjust the solid content to 60%, and stir at 400 r / min for 30 min to obtain a functional composite binder;

[0052] (3) Preparation of mixture

[0053] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2), the addition amount of the functional composite binder in the corn stalk charcoal powder is 12wt.%, and the mixture is ground by 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 into a mold preheated to 185°C, and is pressed at a pressure of 120 MPa for 2 min, and then the hot-pressed block is placed into a tube furnace again, and oxygen is removed by introducing nitrogen gas with a purity of ≥99.99% for 15 min, and then the temperature is increased to 220±10°C at a rate of 5°C / min, and is kept for 1.5 h, and then the temperature is cooled to room temperature by introducing nitrogen gas, to obtain a corn stalk charcoal fuel; the finished product is sealed and stored to prevent moisture.

[0056] Example 2

[0057] A method for preparing a corn stalk charcoal fuel based on a functional composite binder, specifically comprising the following steps:

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

[0059] a. Pretreatment: After removing impurities from the corn stalk waste, the corn stalk waste is dried in an oven at 75±5°C for 16 h, and then is crushed by a crusher to a particle size of ≤0.16 mm, and is then dried in an electric heat air drying oven at 105±2°C to a constant weight;

[0060] b. Atmosphere-protected carbonization: The pretreated stalk powder is loaded into a crucible and placed into a tube furnace, and oxygen is removed by introducing nitrogen gas with a purity of ≥99.99% for 30 min, and then the temperature is increased to 500±10°C at a rate of 5°C / min, and is kept for 4 h; after the end of the heat preservation, the temperature is naturally cooled to room temperature by continuing to introduce nitrogen gas, and the obtained corn stalk charcoal powder is taken out and sealed for storage;

[0061] (2) Preparation of a functional composite binder

[0062] Phosphoric acid and polysilicic acid are mixed at a mass ratio of 8:1, and the pH is adjusted to 3.5±0.2 by using a 29wt.% ammonium hydroxide solution, and then is calcined in a muffle furnace at 600±20°C for 4 h, and is ground to a particle size of ≤3μm after cooling, to obtain a phosphorus-silicon dioxide composite powder; the obtained phosphorus-silicon dioxide composite powder is mixed with polyethylene and lignosulfonic acid, and the mass ratio of phosphoric acid, polyethylene and lignosulfonic acid is 8:3:7, and then deionized water is added to adjust the solid content to 70%, and is stirred at 500 r / min for 30 min, to obtain a functional composite binder;

[0063] (3) Preparation of a mixture

[0064] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2), the addition amount of the functional composite binder in the corn stalk charcoal powder is 15 wt.%, and a ball mill is used for grinding 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 is pressed at a pressure of 130 MPa for 2 min, and then the hot-pressed block is placed back into a tube furnace, pure nitrogen with a purity of ≥99.99% is introduced to remove oxygen for 15 min, the temperature is raised to 220±10°C at a rate of 5°C / min, and the temperature is maintained for 1.5 h, and then nitrogen is introduced to cool to room temperature, to obtain corn stalk charcoal fuel; the finished product is sealed and moisture-proof stored.

[0067] Example 3

[0068] A method for making corn stalk charcoal fuel based on a functional composite binder, specifically comprising the following steps:

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

[0070] a. Pretreatment: After removing impurities from corn stalk waste, dry it in an oven at 75±5°C for 12 h, then crush it to a particle size of ≤0.16 mm with a crusher, and then dry it to a constant weight in an electric heat air drying oven at 105±2°C;

[0071] b. Atmosphere-protected carbonization: The pretreated stalk powder is loaded into a crucible and placed in a tube furnace, pure nitrogen with a purity of ≥99.99% is introduced to remove oxygen for 20-30 min, the temperature is raised to 500±10°C at a rate of 10°C / min, and the temperature is maintained for 4 h; after the temperature maintenance is completed, the nitrogen is continuously introduced to naturally cool to room temperature, and then the product is taken out and sealed for storage, to obtain corn stalk charcoal powder;

[0072] (2) Preparation of functional composite binder

[0073] Phosphoric acid and polysilicic acid are mixed in a mass ratio of 8:4, a 29 wt.% ammonium hydroxide solution is used to adjust the pH to 3.5±0.2, and then calcination is performed in a muffle furnace at 600±20°C for 4 h, and after cooling, the product is ground to a particle size of ≤3 μm to obtain a phosphorus-silicon dioxide composite powder; the obtained phosphorus-silicon dioxide composite powder is mixed with polyethylene and lignosulfonic acid, wherein the mass ratio of phosphoric acid, polyethylene and lignosulfonic acid is 8:3:7, and then deionized water is added to adjust the solid content to 60%, and stirring is performed at 300 r / min for 30 min to obtain a functional composite binder;

[0074] (3) Preparation of mixture

[0075] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2), the addition amount of the functional composite binder in the corn stalk charcoal powder is 10 wt.%, and the mixture is ground by 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 into a mold preheated to 200°C, and is pressed at a pressure of 100 MPa for 2 min, and then the hot-pressed block is placed into a tube furnace again, and nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 15 min, and the temperature is increased to 220±10°C at a rate of 5°C / min, and is kept for 1.5 h, and then nitrogen gas is introduced to cool to room temperature, to obtain corn stalk charcoal fuel; the finished product is sealed and moisture-proof stored.

[0078] Example 4

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

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

[0081] a. Pretreatment: After removing impurities from the corn stalk waste, the corn stalk waste is dried in an oven at 75±5°C for 13 h, and then is crushed by a crusher to a particle size of ≤0.16 mm, and is then dried in an electric heat air drying oven at 105±2°C to a constant weight;

[0082] b. Atmosphere-protected carbonization: The pretreated stalk powder is loaded into a crucible and placed into a tube furnace, nitrogen gas with a purity of ≥99.99% is introduced to remove oxygen for 30 min, the temperature is increased to 500±10°C at a rate of 6°C / min, and is kept for 4 h; after the end of the heat preservation, the nitrogen gas is continuously introduced to cool to room temperature naturally, and the obtained corn stalk charcoal powder is taken out and sealed for storage;

[0083] (2) Preparation of functional composite binder

[0084] Phosphoric acid and polysilicic acid are mixed at a mass ratio of 8:3, and a 29 wt.% ammonium hydroxide solution is used to adjust the pH to 3.5±0.2, and then the mixture is calcined in a muffle furnace at 600±20°C for 4 h, and after cooling, the mixture is ground to a particle size of ≤3 μm to obtain a phosphorus-silicon dioxide composite powder; the obtained phosphorus-silicon dioxide composite powder is mixed with polyethylene and lignosulfonic acid, and the mass ratio of phosphoric acid, polyethylene and lignosulfonic acid is 8:3:7, and then deionized water is added to adjust the solid content to 66%, and the mixture is stirred at 380 r / min for 30 min to obtain a functional composite binder;

[0085] (3) Preparation of mixture

[0086] The corn stalk charcoal powder obtained in step (1) is mixed with the functional composite binder obtained in step (2), the functional composite binder is added in the corn stalk charcoal powder in an amount of 13 wt.%, and the mixture is ground by 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 is pressed at a pressure of 110 MPa for 2 min, and then the hot-pressed block is placed back into a tube furnace, oxygen is discharged by introducing nitrogen gas with a purity of ≥99.99% for 15 min, the temperature is raised to 220±10°C at a rate of 5°C / min, and the temperature is maintained for 1.5 h, and then the temperature is cooled to room temperature by introducing nitrogen gas, to obtain corn stalk charcoal fuel; the finished product is sealed and stored to prevent moisture.

[0089] Comparative Example 1

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

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

[0092] Comparative Example 2

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

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

[0095] Comparative Example 3

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

[0097] After the corn stalk waste is decontaminated, it is dried in an oven at 75±5°C for 14 h, and then crushed by a crusher to a particle size of ≤0.16 mm, and then dried to a constant weight in an electric heating air drying oven at 105±2°C to obtain corn stalk powder.

[0098] Comparative Example 4

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

[0100] The mixture obtained in step (3) was placed in a mold preheated to 100°C, and pressure was maintained at 80 MPa for 2 min, after which the hot-pressed block was placed back into a tube furnace, oxygen was removed by passing in nitrogen with a purity of ≥99.99% for 15 min, and the temperature was raised to 220±10°C at a rate of 5°C / min, and the temperature was maintained for 1.5 h, and then nitrogen was passed to cool to room temperature, to obtain corn straw charcoal fuel; the finished product was sealed and stored to prevent moisture.

[0101] Performance test

[0102] Test object: corn straw charcoal fuel prepared in Examples 1-4 and Comparative Examples 1-4.

[0103] Molding performance: density was determined according to GB / T25211-2010 “Biomass Solid Molding Fuel Test Method”; anti-shatter property was determined according to GB / T25211-2010, and the mass fraction of particles with a particle size of >3 mm was determined after free falling from a height of 1.5 m for 3 times; durability was determined according to GB / T18856.1-2019 “Coal Water Slurry Test Method Part 1: Sampling”, and the proportion of unbroken particles was determined after the drum test.

[0104] Combustion performance: ignition temperature and burnout temperature were determined using a thermal gravimetric analyzer (heating rate 10°C / min, air atmosphere); heat output was determined using an oxygen bomb calorimeter according to GB / T30727-2014 “Solid Biomass Fuel Heat Output Determination Method”.

[0105] Environmental performance: slagging rate was determined according to GB / T1574-2007 “Coal Ash Composition Analysis Method”, and the mass fraction of molten slag was determined after combustion under a blast intensity of 0.2 m / s; sulfur (S) and nitrogen (N) contents were determined using an elemental analyzer according to GB / T28732-2012 “Solid Biomass Fuel Total Sulfur Determination Method”.

[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] Density (g / cm 3 )]]> Shatter resistance (%) Durability (%) Ignition temperature (°C) Burn-out temperature (°C) Heat of combustion (kJ·kg -1 ) Clogging rate (%) S content (%) N content (%) Example 1 1.12 95.3 83.6 392.1 512.4 19150 1.48 0.12 0.35 Example 2 1.08 92.7 80.5 389.5 515.7 18920 1.65 0.13 0.37 Example 3 1.05 90.2 78.3 387.8 518.2 18760 1.72 0.12 0.36 Example 4 1.10 93.8 81.7 390.4 514.1 19030 1.55 0.11 0.34 Comparative Example 1 0.98 82.5 70.1 393.2 521.6 18680 1.83 0.12 0.35 Comparative Example 2 1.01 85.3 73.4 385.7 525.9 18540 3.26 0.13 0.36 Comparative Example 3 0.82 68.4 55.7 298.5 602.3 10230 8.75 0.15 0.42 Comparative Example 4 0.95 78.6 67.9 386.3 530.1 18470 2.15 0.12 0.35

[0109] As can be seen from Table 1, the molding density, anti-shatter property, and durability of Example 1 are the highest; the phosphorus-silicon synergistic effect is fully realized, the slagging rate is as low as 1.48%, and the high-carbon charcoal powder ensures a heat output of 19150 kJ·kg -1 . Examples 2-4 all meet the use requirements. The reasons for the performance degradation of the comparative examples are:

[0110] Comparative Example 1 (binder not calcined): no phosphorus-silicon composite powder formed by calcination, weak interface bonding force between the binder and the carbon powder, resulting in a decrease in the molding density to 0.98 g / cm 3 , the anti-crushing property and the durability were only 82.5% and 70.1%, respectively;

[0111] Comparative Example 2 (lack of polysilicic acid): no polysilicic acid involved, no phosphorus-silicon synergistic de-slagging effect, the slagging rate increased to 3.26%, and the molding skeleton was insufficiently supported, the anti-crushing property was only 85.3%;

[0112] Comparative Example 3 (not carbonized): directly using dry straw powder for molding, no high-carbon carbon structure formed, the calorific value decreased to 10230 KJ·kg -1 , and the raw material impurities were many, resulting in a slagging rate of 8.75%, and the molding performance was overall deteriorated;

[0113] Comparative Example 4 (low hot-pressing parameters): the hot-pressing temperature of 100℃ did not reach the melting interval of polyethylene, and the pressure of 80 MPa was insufficient, the molding body had poor compactness, the density was 0.95 g / cm 3 , the anti-crushing property was only 78.6%, and the oxygen permeation was uneven during combustion, resulting in an increase in the burnout temperature to 530.1℃.

[0114] The above are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection 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 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.

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:

7.

3. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 2, characterized in that, 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.

4. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 3, 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%.

5. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 1, characterized in that, 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.

6. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 1, characterized in that, The corn stalk charcoal powder is prepared by pre-treating and carbonizing corn stalk waste.

7. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 6, characterized in that, The pretreatment steps are 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.

8. The method for producing charcoal fuel from corn stalks based on a functional composite binder according to claim 6, 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.

9. 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.%.

10. A corn stalk charcoal fuel prepared by the method according to any one of claims 1-9.