Formula and preparation method of granular fuel with high tobacco straw content and high slagging resistance

Abstract

The invention discloses a high-tobacco-straw-content and high-slagging-resistance granular fuel formula and a preparation method thereof, and belongs to the technical field of biomass solid fuel. The granular fuel is prepared from the following raw materials in percentage by weight: 60-70% of tobacco straws, 28-38% of fruit sawdust and 2% of magnesium oxide. In order to solve the core problem that the tobacco straws are difficult to be directly fueled at high content, through specific compatibility, a binary synergistic anti-slagging mechanism that a physical melting-resistant framework is constructed by high-calcium fruit sawdust and chemical potassium fixation is realized by magnesium oxide in a fixed proportion is initiated. According to the scheme, the ash melting point softening temperature (ST) of the granular fuel is increased to 1350 DEG C or above and the ash content is reduced to 10% or below while the mass ratio of the tobacco straws is ensured to be up to 60% or above, the dosage of the additive strictly meets the industrial specification of being smaller than or equal to 2%, unification of'high content 'and'high slagging resistance' is achieved, and the method is suitable for industrial production. And a special technical scheme is provided for tobacco companies to treat straw wastes and produce high-value fuels.

Description

Technical Field

[0001] This invention relates to the field of biomass energy and solid waste resource utilization technology, specifically to a biomass pellet fuel formulation and its industrial preparation method that is specifically designed for the tobacco industry, enabling high-proportion utilization of tobacco straw and possessing extremely high anti-caking performance. Background Technology

[0002] my country's tobacco industry generates tens of millions of tons of tobacco straw annually. For tobacco companies, this straw is both agricultural waste urgently needing disposal and a potential biomass resource. Converting tobacco straw into pellet fuel is one of the optimal paths to achieve its large-scale, clean, and high-value utilization, aligning with the tobacco industry's strategic need for green and circular development. However, tobacco companies face a prominent technical contradiction in this area: to achieve large-scale straw utilization, a high tobacco straw content in the fuel is essential; however, the inherent high ash and potassium-chlorine content of tobacco straw results in a fuel with an extremely low ash melting point, making it prone to severe slagging during combustion in boilers, rendering it unsafe to use. This contradiction has become the core obstacle restricting the industrialization of tobacco straw energy utilization.

[0003] In existing technologies, the common method to reduce the risk of slagging is to blend in a large amount of high-quality woody raw materials or use a high proportion of additives. However, this directly reduces the tobacco straw content to below 50%, which cannot meet the needs of tobacco companies for large-scale straw disposal. If a high content is to be maintained, the fuel quality will be low, posing operational risks. Therefore, the industry urgently needs a proprietary technology that can simultaneously achieve the two key objectives of "high tobacco straw content" and "high fuel anti-slagging properties," thereby truly opening up the technological channel from tobacco waste to high-quality commercial fuel. Summary of the Invention

[0004] The purpose of this invention is to provide tobacco companies with a proprietary technical solution to resolve the aforementioned industry contradictions. Specifically, this invention provides a high-tobacco straw content, high-anti-caking pellet fuel formulation and its preparation method. This solution can produce high-quality pellet fuel with an ash melting point softening temperature (ST) of not less than 1350℃ and an ash content of not more than 10%, while ensuring that the tobacco straw content is as high as 60-70%, and the amount of additives is strictly controlled within the compliant range of 2%.

[0005] To achieve the aforementioned objectives of possessing both "high content" and "high anti-slagging properties," the present invention adopts the following technical solution: A high-tobacco straw content, high-anti-caking pellet fuel is produced from the following raw materials by a specific process in the following weight percentages: Tobacco straw: 60% to 70%, Fruit wood chips: 28% to 38%, Magnesium oxide: 2%.

[0006] To achieve efficient anti-slagging performance and meet the challenges posed by high ash content, the calcium oxide (CaO) content in the ash of the wood chips must be greater than 30 wt.%. The resulting pellet fuel must simultaneously meet the following requirements: ash melting point softening temperature (ST) not lower than 1350℃, and ash content not higher than 10%.

[0007] Preferably, the ash content of the tobacco straw contains more than 15 wt.% potassium oxide (K2O) to clarify the characteristics of the raw material targeted by this scheme. The wood chips are preferably apple, pear, or peach wood chips with high calcium content. The magnesium oxide has a purity of ≥90% and is preferably 250-325 mesh to ensure dispersion and reaction efficiency.

[0008] The above-mentioned method for preparing pellet fuel mainly includes the following steps: raw material pretreatment, precise proportioning and mixing, extrusion molding, cooling and sieving.

[0009] Technical principles and inventive contributions of this invention: The core of this invention lies in breaking through the industry consensus that "high content inevitably leads to a sharp increase in the risk of slagging" through an original component synergistic design.

[0010] 1. High-calcium fruitwood chips construct a high-strength physical melt-resistant skeleton: To achieve high anti-slagging properties, this invention does not simply use ordinary wood chips, but specifically selects fruitwood chips with an ash CaO content >30%. When mixed with 60-70% tobacco straw at a ratio of 28-38%, it forms an ash mineral skeleton mainly composed of high-melting-point calcium aluminum silicates after combustion. This skeleton can not only withstand higher temperatures, but also effectively prevent the flow and aggregation of low-melting-point substances, providing a basic anti-melting guarantee for the "high content" system.

[0011] 2. Precise Chemical Potassium Fixation through "2% Magnesium Oxide Fixation": To address the significant potassium content introduced from high-content tobacco straw, this invention employs 2% magnesium oxide as a chemical fixative. During combustion, this proportion of magnesium oxide reacts efficiently with K₂O and SiO₂ to generate forsterite (Mg₂SiO₄), which has a melting point as high as 1890℃. This permanently fixes the primary slagging factor, potassium, into the high-melting-point mineral through chemical means. The 2% dosage, after optimization, represents the minimum effective threshold for fundamentally transforming the slagging risk in high-content systems while meeting stringent additive compliance requirements (≤2%).

[0012] 3. Synergistic Effect Achieves Dual Objectives: The "high-calcium skeleton" and "chemical potassium fixation" do not work independently, but rather synergistically. The "skeleton" improves the overall ash content and lowers the refractoriness threshold while diluting harmful components, while "potassium fixation" eliminates key factors that lead to melting. This synergy allows the final product to achieve excellent anti-slagging performance (ST≥1350℃) even with a tobacco straw content as high as 60-70%, which is unpredictable with conventional technologies.

[0013] This invention provides tobacco companies with a clear technical path: by using their abundant tobacco straw resources, combined with a specific proportion of localized fruit wood waste and a small amount of compliant additives, they can produce exclusive fuel with performance superior to ordinary wood pellets on the market, which has significant environmental, economic and strategic benefits. Attached Figure Description

[0014] Figure 1 This is a flow chart of the preparation process of the high tobacco straw content and high anti-caking pellet fuel described in this invention. As shown in the figure, the process mainly includes: raw material pretreatment (drying and crushing), precise batching and mixing, extrusion molding, cooling and sieving, and other steps. Detailed Implementation

[0015] The following examples further illustrate the technical solution of the present invention and the dual effects of "high content" and "high anti-slagging properties" that it can achieve. Experimental methods not specifically described in the examples are generally performed according to conventional conditions in the art.

[0016] Example 1: High-content performance formulation Raw material ratio (by weight): tobacco straw 70%, apple wood chips 28%, magnesium oxide 2%.

[0017] Preparation: Tobacco straw and apple sawdust are dried to a moisture content of approximately 13%, and then pulverized separately to pass through a 3mm sieve and a 2mm sieve, respectively. The raw materials are accurately weighed according to the above proportions and added to a mixer, where they are mixed for 20 minutes. The uniformly mixed material is then fed into a ring die pellet mill (compression ratio 5.5:1) for extrusion and pelletizing. The pellets are cooled and sieved to obtain finished pellet fuel with a diameter of 6-8mm.

[0018] Test results: Moisture content 8.5%; Calorific value 15.04 MJ / kg; Ash content 9.8%; Ash melting point: Deformation temperature (DT) 1242℃, softening temperature (ST) 1367℃, hemispherical temperature (HT) 1449℃, flow temperature (FT) >1500℃; Total additives: 2%. The data shows that at a high content of 70%, its key anti-slagging indicator (ST) far exceeds the industrial safety operation standard (typically ≥1150℃), achieving a balance between high content and high anti-slagging properties.

[0019] Example 2: Optimized Overall Performance Formula Raw material ratio (weight %): tobacco straw 60%, apple wood chips 38%, magnesium oxide 2%.

[0020] The preparation steps are the same as in Example 1.

[0021] Test results: Moisture content 8.2%; Calorific value 15.35 MJ / kg; Ash content 8.6%; Deformation temperature (DT) 1265℃, softening temperature (ST) 1384℃, hemispherical temperature (HT) 1473℃, flow temperature (FT) >1500℃. This formulation achieves higher calorific value, lower ash content, and better anti-caking properties while maintaining a high tobacco straw content, representing the optimal balance between overall performance and raw material cost.

[0022] Summary of the technical effects of this invention Both formulations provided in this invention successfully achieved their intended objectives. Their common feature is that, with a tobacco straw content of no less than 60%, the ash melting point softening temperature (ST) of the prepared pellet fuel is significantly higher than 1350℃, and the ash content is less than 10%, while the amount of magnesium oxide additive is strictly fixed at 2%. This fully verifies the effectiveness of the synergistic technology system of "60-70% tobacco straw + 28-38% high-calcium fruitwood chips + 2% magnesium oxide" claimed in this invention. This system is specifically designed for tobacco companies, enabling them to maximize the utilization of their own tobacco straw waste while producing high-performance, compliant pellet fuel with market competitiveness. It solves the core contradiction that has long plagued industrialization—the difficulty in balancing "content" and "quality"—and possesses clear industrialization prospects and outstanding practicality.

[0023] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A high-tobacco straw content, high-anti-caking pellet fuel, characterized in that, It is made from the following raw materials by weight percentage: 60% to 70% tobacco straw, 28% to 38% fruit wood chips, and 2% magnesium oxide; the ash content of the fruit wood chips is greater than 30 wt.%; the ash melting point softening temperature of the pellet fuel is not lower than 1350℃, and the ash content is not higher than 10%.

2. The high tobacco straw content, high anti-caking pellet fuel according to claim 1, is characterized in that: The ash content of the tobacco straw contains more than 15 wt.% potassium oxide.

3. The high tobacco straw content, high anti-caking pellet fuel according to claim 1, characterized in that: The wood chips are pulverized apple wood, pear wood, or peach wood.

4. The high tobacco straw content, high anti-caking pellet fuel according to claim 1, characterized in that: The purity of the magnesium oxide is not less than 90%, and the particle size is preferably 250 mesh to 325 mesh.

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