Composite coal and preparation method thereof
By incorporating charcoal powder and other ingredients into pulverized coal, the problems of high sulfide emissions and high ignition temperature during briquette combustion have been solved, achieving the effects of low emissions, high-efficiency combustion, and increased strength.
Patent Information
- Application Number
- CN202511044638.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-11-14
AI Technical Summary
The existing technology faces the dual technical bottlenecks of high sulfide emissions and high ignition temperature during the combustion of coal briquettes, making it difficult to achieve systematic optimization of sulfur control and combustion activation energy across the entire combustion chain.
Charcoal powder, binder, sulfur fixative, combustion promoter, etc. are added to pulverized coal. The high fixed carbon and low sulfur characteristics of charcoal powder reduce sulfur emissions and ignition temperature, and the binder and promoter optimize the combustion process.
It effectively reduces sulfur emissions and ignition temperature, achieves efficient combustion, lowers the ignition temperature to 350-400℃, and improves combustion intensity and mechanical strength.
Smart Images
Figure CN120944601A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a fuel, specifically to a composite coal and its preparation method. Background Technology
[0002] Existing coal briquettes generally face the dual technical bottlenecks of high sulfide emissions and high ignition temperature during combustion.
[0003] First, sulfide emissions originate from the conversion of sulfur in coal into gaseous pollutants such as SO2 and SO3 at high temperatures. SO2 emission concentrations in industrial boilers and residential coal applications often exceed 500 mg / m³, far surpassing environmental limits. Second, the high ignition temperature of briquettes is mainly attributed to delayed volatile matter release and the combustion activation energy barrier.
[0004] Current technologies often employ single improvement methods, such as extensive mechanical mixing of combustion promoters leading to uneven dispersion, or reliance on inefficient desulfurizers, making it difficult to achieve full-chain sulfur control (e.g., the coexistence of FeS2 and SO2 / Na reaction pathways), and lacking systematic optimization of component synergistic effects and reaction kinetics. Summary of the Invention
[0005] To address the technical problems of high sulfide emissions and high ignition temperature that existing briquettes generally face during combustion, this invention provides a composite briquette and its preparation method. By adding charcoal powder to coal powder, the high fixed carbon and low sulfur characteristics of charcoal powder are utilized to reduce sulfur emissions. At the same time, the ignition temperature of charcoal powder is lower than that of coal powder, which can greatly reduce the ignition temperature of the composite briquette.
[0006] The technical solution of this invention is: A composite coal briquette comprises 17%-22% charcoal powder, 11%-15% binder, 1.5%-2% sulfur fixative, 0.5%-1% combustion promoter, 1%-2% bentonite, and 1%-2% carbide slag; The rest is pulverized coal.
[0007] Optionally, the adhesive comprises 7%-9% inorganic adhesive and 4%-6% organic adhesive.
[0008] Optionally, the inorganic binder includes fly ash, carbide slag, sodium sulfate, and silica fume; The ratio of fly ash: carbide slag: sodium sulfate is 7:3:0.5.
[0009] Optionally, the organic binder includes carboxymethylated corn starch and waste oil microcapsules; Carboxymethylated corn starch: waste oil microcapsules = 3:1.
[0010] Optionally, the outer layer of the composite coal has a higher content of charcoal powder than the coal powder content, and the inner layer of the composite coal has a lower content of charcoal powder than the coal powder content. The outer layer of the composite coal has a thickness ranging from 0.5 mm to 1 mm from its outer surface to its middle.
[0011] A method for preparing composite coal includes the following steps: S10. Raw material pretreatment, preparation of coal powder and charcoal powder, activation of coal powder and supercritical water treatment of charcoal powder, and preparation according to the ratio of the inner and outer layers of composite coal; S20. Prepare a binder by mixing fly ash, carbide slag, and sodium sulfate in a ratio of 7:3:0.5, then mixing it with carboxymethylated corn starch, and then adding waste oil microcapsules to form a uniform slurry. S30, high pressure molding: after the raw materials are mixed with binder, they are high pressure molded according to the inner and outer layer structure of composite coal, and microwave preheating is used simultaneously to activate the binder activity. S40, post-processing: the formed composite coal is solidified in a nitrogen tunnel, and carbon dioxide is introduced into the nitrogen channel.
[0012] Optionally, in the raw material pretreatment of step S10, the particle size of the coal powder is less than or equal to 0.5 mm, and the particle size of the charcoal powder is less than or equal to 0.3 mm. The prepared inner and outer layer raw materials were soaked in a 5% NaOH solution for 2 hours and then dried until the moisture content was less than 3%.
[0013] Optionally, in step S20, the mixed fly ash, carbide slag, sodium sulfate and carboxymethylated corn starch are mixed in a mass ratio of 1.5-1.75. The waste oil microcapsule includes an outer shell and waste oil located inside the outer shell. The waste oil needs to be filtered, desulfurized, and deacidified. The outer shell material is a high molecular polymer. The waste oil is formed by an interfacial reaction between the waste oil and the aqueous phase containing polymer monomers to form a shell and encapsulate the waste oil.
[0014] Optionally, in step S40, the temperature in the nitrogen tunnel is 120°C, the curing time is at least 30 minutes, and the carbon dioxide flow rate is 0.5 L / min.
[0015] Optionally, the sulfur fixative is powdered coal gangue, which is leached with 5%-10% sulfuric acid or hydrochloric acid and then calcined at a temperature of 700℃-900℃. The combustion accelerator is potassium nitrate.
[0016] Compared with the prior art, the beneficial effects of the present invention are: By adding charcoal powder to pulverized coal, the high fixed carbon and low sulfur content of charcoal powder can reduce sulfur emissions. At the same time, the ignition temperature of charcoal powder is lower than that of pulverized coal, which can greatly reduce the ignition temperature of the composite coal.
[0017] In addition, sulfur emissions can be further reduced by adding sulfur fixatives. Adding combustion promoters reduces the activation energy of volatile matter release in composite coal, lowering the ignition temperature to 350-400℃. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of the structure of composite coal; Figure 2 This is a schematic diagram of the steps involved in preparing composite coal briquettes.
[0020] Figure label: 10. Composite coal; 11. Outer layer; 12. Inner layer. Detailed Implementation
[0021] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.
[0022] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.
[0023] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0024] Example 1
[0025] See Figure 1This embodiment discloses a composite coal briquette 10, which includes 17%-22% charcoal powder, 11%-15% binder, 1.5%-2% sulfur fixative, 0.5%-1% combustion promoter, 1%-2% bentonite and 1%-2% carbide slag, with the remainder being coal powder.
[0026] Charcoal powder has the characteristics of high fixed carbon and low sulfur, with a carbon content of more than 85% and a sulfur content of less than 0.1%. At the same time, the ignition temperature of charcoal powder is lower than that of coal powder. Therefore, in the initial stage of ignition, the charcoal powder with a low ignition temperature can be used to burn first, and then the coal powder can be ignited by the charcoal powder to achieve the purpose of complete combustion.
[0027] The binder mentioned above includes 7%-9% inorganic binder and 4%-6% organic binder. By adding the binder, the shape of the composite coal 10 is kept stable.
[0028] In addition, inorganic binders include fly ash, carbide slag, sodium sulfate, and silica fume, with a fly ash:carbide slag:sodium sulfate ratio of 7:3:0.5.
[0029] Among them, fly ash has a glassy structure and is rich in SiO2 and Al2O3, which provide a silica-alumina phase for the binder. The glassy structure dissociates in an alkaline environment to generate active aluminosilicate monomers, which form a three-dimensional silicon-oxygen-alumina-oxygen network through polycondensation reaction. Furthermore, the unreacted fly ash can fill the pores of the composite coal 10, optimize the density, and improve the compressive strength.
[0030] Calcium carbide slag is rich in calcium oxide, which reacts with water to form calcium hydroxide, providing a strongly alkaline environment that promotes the dissociation of the glassy structure in fly ash. Furthermore, during combustion, calcium hydroxide reacts with sulfides to form calcium sulfate, thus reducing sulfur emissions.
[0031] Sodium sulfate, as a basic activator, promotes the dissolution of acid salts by increasing the energy level of sodium ions, thus shortening the setting time. Furthermore, it can introduce sulfate and calcium ions to form a microcrystalline structure, reducing the porosity of composite coal 10 and inhibiting shrinkage cracking.
[0032] Silica fume can fill the gaps between particles. Its high specific surface area promotes the interfacial reaction between fly ash, carbide slag, sodium sulfate and coal particles, thereby improving compressive strength.
[0033] The organic binder comprises carboxymethylated corn starch and waste oil microcapsules, with a carboxymethylated corn starch:waste oil microcapsule ratio of 3:1. The viscosity properties of the carboxymethylated corn starch enhance the binder's flowability, ensuring uniform coverage of the particle surface. By introducing carboxymethyl groups, the carboxymethylated corn starch strengthens the hydrogen bonding and electrostatic adsorption between starch molecules and coal powder particles, thereby improving the cold compressive strength of composite coal 10.
[0034] Corn starch decomposes at high temperatures to produce carbon monoxide and volatile hydrocarbons, which promotes the initial combustion reaction of composite coal 10, reduces the ignition temperature of composite coal 10, and enhances the later combustion efficiency of composite coal 10 through the residual carbon skeleton.
[0035] Waste oil microcapsules use waste oils such as polyurethane or chitosan as the outer shell, and encapsulate reducing agents such as urea and NH3 precursors inside. During combustion, the shell ruptures at high temperatures (300-500℃), releasing the internal substances. NH3 then undergoes a selective non-catalytic reduction reaction with nitrogen oxides in the flue gas, thereby reducing nitrogen oxide emissions.
[0036] Waste oil is used as the core material of the capsule. Its high calorific value participates in the combustion process, compensating for the calorific value loss caused by the binder, while avoiding environmental pollution from the direct discharge of waste oil.
[0037] In addition, carboxymethyl starch provides cold strength, and the thermal decomposition residue of waste oil microcapsules supplements the structural support at high temperatures, thereby increasing the thermal strength of composite coal 10 and making carboxymethyl corn starch and waste oil microcapsules complementary.
[0038] In one preferred embodiment: The outer layer 11 of the composite coal briquette 10 has a higher content of charcoal powder than coal powder, and the inner layer 12 of the composite coal briquette 10 has a lower content of charcoal powder than coal powder. The outer layer 11 of the composite coal briquette 10 has a thickness of 0.5 mm to 1 mm from its outer surface to its middle.
[0039] In this composite coal briquette 10, the outer layer 11 contains a maximum of 25% charcoal powder, which, combined with a combustion promoter, enables rapid ignition. The high fixed carbon and low sulfur content of the charcoal powder enhances the reactivity of the outer layer 11 structure during the initial ignition phase of the composite coal briquette 10. With a porosity greater than 60% and a specific surface area greater than 800 m² / g, the charcoal powder rapidly absorbs oxygen and releases volatiles during the initial ignition phase, creating a localized high-temperature environment that lowers the overall ignition temperature of the composite coal briquette 10 to 350-400℃.
[0040] The inner layer contains 70% or more coal powder, providing approximately 50%-70% fixed carbon. Through the action of the binder, it forms a dense structure, slows down the rate of oxygen penetration, and prolongs the combustion time.
[0041] By complementing the rapid ignition of the outer 11 layer of charcoal powder with the sustained combustion characteristics of the inner 12 layer of coal powder, and by combining the alkaline oxides and sulfur fixatives contained in the charcoal powder, a balance of "high-efficiency combustion, low emissions, and high strength" is achieved.
[0042] In this embodiment, the sulfur fixative is modified powdered coal gangue, with an aluminum oxide content of ≥40%, resulting in a specific surface area of 800 m² / g and a sulfur fixation efficiency of over 85%. Furthermore, the ferric oxide on its surface enhances the ability to capture sulfur free radicals through a redox synergistic effect. Therefore, this sulfur fixative achieves efficient desulfurization through a dual mechanism of chemical transformation and physical adsorption.
[0043] The combustion promoter mentioned above is potassium nitrate. Potassium nitrate can decompose into oxygen and potassium nitrite in a high-temperature environment of 300-500℃, releasing active oxygen. The released gaseous products (oxygen and nitrogen oxides) enhance the diffusion rate of gas in the fuel pores and improve the permeation efficiency of active oxygen.
[0044] Active oxygen directly participates in the oxidation reaction of carbon-based fuels, shortens the ignition delay time of volatiles, and promotes the fuel oxidation reaction. This process can significantly reduce the ignition temperature of the composite coal 10, generally reducing the ignition point of pulverized coal from 550℃ to 350-400℃.
[0045] In addition, the potassium ions generated by the decomposition of potassium nitrate can react with aluminum oxide in coal ash (the product of the combustion of composite coal 10) to form potassium aluminum sulfate complex, which inhibits the release of sulfur oxides and raises the melting point of coal ash to above 1200℃, thereby reducing the risk of coal ash slagging.
[0046] The main component of bentonite is montmorillonite, accounting for about 85%-90%, along with minor minerals and impurities (including quartz, quartzite, feldspar, etc.). Montmorillonite is a layered silicate mineral, and its crystal structure consists of two layers of silicon-oxygen tetrahedra sandwiching a layer of aluminum-oxygen octahedra. The layers are connected by exchangeable cations, and the surface carries a negative charge, which gives it ion exchange capacity.
[0047] Adding 1%-2% bentonite to the composite coal 10 can improve its mechanical strength. Bentonite can expand 20-30 times its original volume after absorbing water, forming a gel network during the mixing process. This network fills the gaps between the composite coal 10 particles and coats the particle surface, enhancing the cohesion between the particles.
[0048] During the combustion process, although the interlayer structure of the bentonite is partially destroyed, its residual aluminosilicates can still serve as a skeleton support, reducing the risk of hot-state cracking of the composite coal 10.
[0049] The highly alkaline waste residue produced during the hydrolysis of calcium carbide in the industrial production of polyvinyl chloride (PVC) from calcium carbide slag mainly consists of calcium hydroxide and calcium carbonate, with small amounts of oxides such as SiO2, Al2O3, and Fe2O3. Upon dissolution, the calcium hydroxide in the calcium carbide slag releases hydroxide ions, promoting the dissolution of the silica-alumina phase in raw materials such as pulverized coal, forming a silicate and chlorate network structure, and enhancing the compressive strength of the composite coal 10.
[0050] In addition, during the combustion process, calcium hydroxide and sulfur oxides in the carbide slag react to form calcium sulfate, which can play a role in sulfur fixation.
[0051] Example 2
[0052] See Figure 2 This embodiment discloses a method for preparing the composite coal of Example 1, specifically including the following steps: S10. Raw material pretreatment, preparation of coal powder and charcoal powder, activation of coal powder and supercritical water treatment of charcoal powder, and preparation according to the ratio of inner layer 12 and outer layer 11 of composite coal 10.
[0053] One method for activating pulverized coal is to impregnate it in a 5% NaOH solution. Activated pulverized coal achieves enhanced combustion performance, synergistic control of pollutants, and resource recycling through physicochemical modification.
[0054] The raw materials for inner layer 12 and outer layer 11 were soaked in 5% NaOH solution for 2 hours and then dried at 105°C until the moisture content was less than 3%.
[0055] The conditions for supercritical water treatment are: treatment at 374℃ and 22.1MPa for 30 minutes. By treating with supercritical water, the porosity of charcoal powder can be increased to 75%, the specific surface area can reach 800-1000m² / g, and the CO2 adsorption and combustion mass transfer efficiency can be enhanced.
[0056] In the raw material pretreatment, the particle size of coal powder is less than or equal to 0.5 mm, and the particle size of charcoal powder is less than or equal to 0.3 mm.
[0057] S20. Prepare a binder by mixing fly ash, carbide slag, and sodium sulfate in a ratio of 7:3:0.5, then mixing it with carboxymethylated corn starch, and finally adding waste oil microcapsules to form a uniform slurry.
[0058] The mixed fly ash, carbide slag, sodium sulfate and carboxymethylated corn starch are mixed in a mass ratio of 1.5-1.75.
[0059] The waste oil microcapsule includes an outer shell and waste oil located inside the outer shell. The waste oil needs to be filtered, desulfurized, and deacidified. The outer shell material is a high molecular polymer.
[0060] The waste oil is formed by an interfacial reaction between the waste oil and the aqueous phase containing polymer monomers to form a shell and encapsulate the waste oil.
[0061] S30, high pressure molding: After the raw materials are mixed with binder, they are high pressure molded according to the structure of composite coal 10 inner and outer layers 11, and microwave preheating is used to activate the binder activity. S40, post-processing, the formed composite coal 10 is solidified in a nitrogen tunnel, and carbon dioxide is introduced into the nitrogen channel.
[0062] The temperature in the nitrogen tunnel is 120℃, the curing time is at least 30 minutes, and the carbon dioxide flow rate is 0.5L / min.
[0063] The sulfur fixative is powdered coal gangue, which is leached with 5%-10% sulfuric acid or hydrochloric acid and then calcined at a temperature of 700℃-900℃.
[0064] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.
Claims
1. A composite coal briquette, characterized in that, It includes 17%-22% charcoal powder, 11%-15% binder, 1.5%-2% sulfur fixative, 0.5%-1% combustion promoter, 1%-2% bentonite, and 1%-2% carbide slag; The rest is pulverized coal.
2. The composite coal according to claim 1, characterized in that, The adhesive comprises 7%-9% inorganic adhesive and 4%-6% organic adhesive.
3. The composite coal according to claim 2, characterized in that: The inorganic binder includes fly ash, carbide slag, sodium sulfate, and silica fume; The ratio of fly ash: carbide slag: sodium sulfate is 7:3:0.
5.
4. The composite coal according to claim 2, characterized in that: The organic binder includes carboxymethylated corn starch and waste oil microcapsules; Carboxymethylated corn starch: waste oil microcapsules = 3:
1.
5. The composite coal according to claim 1, characterized in that: The outer layer of the composite coal has a higher content of charcoal powder than the coal powder content, while the inner layer of the composite coal has a lower content of charcoal powder than the coal powder content. The outer layer of the composite coal has a thickness ranging from 0.5 mm to 1 mm from its outer surface to its middle.
6. A method for preparing the composite coal according to any one of claims 1-5, characterized in that, Includes the following steps: S10. Raw material pretreatment, preparation of coal powder and charcoal powder, activation of coal powder and supercritical water treatment of charcoal powder, and preparation according to the ratio of the inner and outer layers of composite coal; S20. Prepare a binder by mixing fly ash, carbide slag, and sodium sulfate in a ratio of 7:3:0.5, then mixing it with carboxymethylated corn starch, and then adding waste oil microcapsules to form a uniform slurry. S30, high pressure molding: after the raw materials are mixed with binder, they are high pressure molded according to the inner and outer layer structure of composite coal, and microwave preheating is used simultaneously to activate the binder activity. S40, post-processing: the formed composite coal is solidified in a nitrogen tunnel, and carbon dioxide is introduced into the nitrogen channel.
7. The preparation method according to claim 6, characterized in that: In the raw material pretreatment of step S10, the particle size of the coal powder is less than or equal to 0.5 mm, and the particle size of the charcoal powder is less than or equal to 0.3 mm. The prepared inner and outer layer raw materials were soaked in a 5% NaOH solution for 2 hours and then dried until the moisture content was less than 3%.
8. The preparation method according to claim 6, characterized in that, In step S20, the mixed fly ash, carbide slag, sodium sulfate and carboxymethylated corn starch are mixed in a mass ratio of 1.5-1.
75. The waste oil microcapsule includes an outer shell and waste oil located inside the outer shell. The waste oil needs to be filtered, desulfurized, and deacidified. The outer shell material is a high molecular polymer. The waste oil is formed by an interfacial reaction between the waste oil and the aqueous phase containing polymer monomers to form a shell and encapsulate the waste oil.
9. The preparation method according to claim 6, characterized in that, In step S40, the temperature in the nitrogen tunnel is 120°C, the curing time is at least 30 minutes, and the carbon dioxide flow rate is 0.5 L / min.
10. The preparation method according to claim 6, characterized in that, The sulfur fixative is powdered coal gangue, which is leached with 5%-10% sulfuric acid or hydrochloric acid and then calcined at a temperature of 700℃-900℃. The combustion accelerator is potassium nitrate.