A solid substitute fuel based on gasified fine slag and a method for producing the same

Abstract

The present application relates to solid waste resource utilization technical field, specifically disclose a kind of solid alternative fuel based on gasification fine slag, by weight parts, including gasification fine slag 10~40 parts, municipal sludge 10~40 parts, byproduct of citrus fruit 30~70 parts, the forming density of the solid alternative fuel is 1.28g / cm 3 , compressive strength is 1.22N / cm 2 And specific energy consumption is 10.65J / g.The specific preparation process includes the following steps: 1) pretreatment is carried out to raw material respectively;2) the pretreated raw material is mixed;3) the mixed raw material is added to granulating equipment and extruded into smooth cylindrical solid alternative fuel.The present application is based on gasification fine slag, adds municipal sludge and biomass to obtain solid alternative fuel, improves the defect that gasification fine slag combustion heat value is not high, and can reduce ash content, so that it meets the conditions of resource utilization, with higher density and compressive strength, facilitate the solid alternative fuel as fuel product transportation and preservation, provide new technical ideas and direction for the use of gasification fine slag.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization, and in particular to a solid alternative fuel based on gasified fine slag and a preparation method thereof. Background Art

[0002] Gasification slag is a solid waste generated during the coal gasification process. Its main hazards lie in its environmental pollution and waste of land resources. With the development of coal gasification technology, the stockpile of gasification slag has continued to increase, causing serious environmental problems. Gasification slag contains incompletely burned carbon residues, metal oxide minerals, and other components. If not properly treated, these components will pollute the environment. Combustion of gasification slag is an effective large-scale treatment method. However, due to its high carbon content, large specific surface area, and well-developed pore structure, gasification slag exhibits low calorific value, incomplete combustion, and high ash content when burned alone. This makes it unsuitable for direct use as fuel. Furthermore, conventional boilers cannot burn gasification slag filter cakes with excessively small particle sizes. Therefore, co-firing gasification slag with raw coal in a certain ratio has become the main treatment method. However, the amount of gasification slag that can be processed each time is limited, and the amount of gasification slag produced far exceeds the amount that can be recycled. This results in an increasing amount of gasification slag and an inability to fully utilize the gasification slag. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the object of the present invention is to provide a solid alternative fuel based on gasified fine slag with good combustion performance, high strength, low energy consumption, small equipment loss and low cost.

[0004] Another object of the present invention is to provide a specific preparation method of the solid alternative fuel based on gasified fine slag.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solution: a solid alternative fuel based on gasified fine slag, which comprises 35 parts of gasified fine slag, 15 parts of municipal sludge, and 50 parts of biomass by weight, and the molding density of the solid alternative fuel is 1.28g / cm 3 , compressive strength is 1.22N / cm 2 and a specific energy consumption of 10.65 J / g.

[0006] This technical solution works by combining sewage sludge and citrus peel to improve the low calorific value of coal gasification fine residue when burned alone, while its low ash content improves the high slagging potential of citrus peel alone, enabling resource utilization. This solid alternative fuel boasts advantages such as high calorific value, high density, strong wear resistance (high compressive strength and wear resistance), low energy consumption, and high combustion potential, making it easy to produce, transport, and use. The invention of this hybrid solid alternative fuel offers new solutions for the disposal of gasification fine residue, sewage sludge, and citrus peel biomass, achieving comprehensive solid waste management.

[0007] Municipal sludge refers to the solid waste generated by sewage treatment plants during the urbanization process when treating domestic and industrial wastewater. Amidst the rapid pace of urbanization and industrialization, the production of excess sludge has become a key obstacle to achieving sustainable social development. Currently, incineration accounts for a significant portion of China's sludge disposal. Sludge is rich in organic matter, typically comprising 40% to 70% of its total weight. This organic matter not only has a high calorific value (8 to 15 MJ / kg on a dry basis), but also demonstrates its potential for energy conversion. While still in its infancy, the conversion of sludge into derivative fuels is increasing annually, currently representing approximately 10% of the total sludge incineration process. Taking these factors into account, it is expected that the conversion of sludge into pelletized fuels will increasingly be adopted in the future, not only because it is more economically sustainable but also because it better meets environmental and policy requirements.

[0008] Citrus peel biomass refers to biomass materials made from citrus fruit peels, pomace, and other byproducts through physical, chemical, or biotechnological methods. In recent years, biomass energy has become a key component of today's new energy sources due to its renewable, environmentally friendly, widespread distribution, and high yield. Solid alternative fuels are compacted and formed using pelletizing equipment, resulting in higher density and combustion stability. These technologies make the energy conversion of solid waste possible, effectively reducing waste volume, lowering pollutant emissions, and alleviating environmental pressure. They can also serve as a clean energy source for heating, power generation, and other sectors, helping to reduce dependence on fossil fuels and promote a green transition in the energy structure.

[0009] In order to better realize the present invention, further, by weight, 35 parts of gasification fine residue, 15 parts of municipal sludge, and 50 parts of citrus fruit by-products.

[0010] In order to better implement the present invention, further, the moisture content of the gasification fine slag, municipal sludge and biomass is less than 10%.

[0011] In order to better realize the present invention, further, the gasification fine slag, urban sludge, and biomass are all powders with a particle size of less than 100 meshes.

[0012] In order to better implement the present invention, further, the biomass is composed of by-products of citrus fruits.

[0013] In order to better implement the present invention, further, the citrus fruit by-product includes citrus fruit peel or citrus fruit residue.

[0014] The above-mentioned method for preparing a solid alternative fuel based on gasified fine slag comprises the following steps:

[0015] (1) Pre-treat the raw materials separately;

[0016] (2) Mixing the pretreated raw materials;

[0017] (3) The mixed raw materials are added to the granulation equipment and extruded into cylindrical solid alternative fuels with smooth surfaces.

[0018] In order to better implement the method of the present invention, further, in the step (3), the extrusion parameters of the granulation equipment for extruding the mixed raw materials into a cylindrical solid alternative fuel with a smooth surface meet at least one of the following conditions:

[0019] a. Extrusion pressure is 40MPa~100MPa;

[0020] b. Extrusion temperature is 80℃~160℃;

[0021] c. Holding time is 200s~400s;

[0022] d. Compression rate is 10 mm / s~30 mm / s.

[0023] In order to better implement the method of the present invention, further, in the step (3), the extrusion parameters of the granulation equipment for extruding the mixed raw materials into a cylindrical solid alternative fuel with a smooth surface meet at least one of the following conditions:

[0024] a. Extrusion pressure is 74.17MPa;

[0025] b. Extrusion temperature is 141.44℃;

[0026] c. Holding time is 400 s;

[0027] d. The compression rate is 11.66 mm / s.

[0028] In order to better implement the method of the present invention, further, in the step (1), the raw materials are pretreated by reducing the moisture content of the gasification fine residue filter cake, urban sludge, and citrus fruit by-products to less than 10% by natural air drying or drying, and then crushing them with a crusher and passing them through a 100-mesh sieve to obtain pretreated gasification fine residue powder, urban sludge powder, and citrus fruit by-product powder.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) The present invention uses gasified fine slag as the basis, and adds municipal sludge and biomass to produce a solid alternative fuel. The solid alternative fuel has good flammability, improves the defect of low combustion calorific value of gasified fine slag, and can reduce the ash content to meet the conditions for resource utilization. It provides a new technical idea and technical direction for the application of gasified fine slag.

[0031] (2) The solid alternative fuel prepared by the present invention has a high density and compressive strength, which facilitates the transportation and storage of the solid alternative fuel as a fuel product;

[0032] (3) The method for preparing solid alternative fuel provided by the present invention uses all waste raw materials, and does not require the addition of additional chemical agents such as treatment agents, adhesives and combustion aids. This achieves resource utilization while turning waste into treasure. In addition, the entire solid alternative fuel production process has low energy consumption and small equipment loss. The prepared solid alternative fuel has high specific energy consumption and low production cost, which is conducive to large-scale investment and industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0034] Figure 1 This is a physical picture of the solid alternative fuel based on gasified fine slag prepared by the present invention;

[0035] Figure 2 This is a scanning electron microscope image of the solid alternative fuel based on gasified fine slag prepared by the present invention;

[0036] Figure 3 TG and DTG curves of the solid alternative fuel based on gasified fine slag prepared in the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, process conditions and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the following embodiments. However, the embodiments of the present invention are not limited thereto. Without departing from the above-mentioned technical ideas of the present invention, various replacements and changes are made according to common technical knowledge and customary means in this field, which should be included in the scope of the present invention. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Example 1:

[0039] This embodiment provides a solid alternative fuel based on gasified fine slag, which comprises 35 parts of gasified fine slag, 15 parts of municipal sludge, and 50 parts of citrus fruit by-products. The molded density of the solid alternative fuel is 1.28 g / cm 3 , compressive strength is 1.22 N / cm 2 and a specific energy consumption of 10.65 J / g.

[0040] The moisture content of the gasification fine residue, urban sewage sludge, and citrus fruit by-products is less than 10%, and the gasification fine residue, urban sewage sludge, and citrus fruit by-products are all powders with a particle size of less than 100 meshes.

[0041] In addition, the citrus fruit by-product includes citrus fruit peel or citrus fruit pomace.

[0042] The method for preparing the solid alternative fuel based on gasified fine slag comprises the following steps:

[0043] (1) Pre-treating the raw materials separately; the pre-treating process of the raw materials is to reduce the moisture content of the gasification fine residue filter cake, urban sewage sludge, and citrus fruit by-products to less than 10% by natural air drying or drying, and then crush them with a crusher and pass them through a 100-mesh sieve to obtain pre-treated gasification fine residue powder, urban sewage sludge powder, and citrus fruit by-product powder;

[0044] (2) Mixing the pretreated raw materials;

[0045] (3) The mixed raw materials are added to the granulation equipment and extruded into cylindrical solid alternative fuels with smooth surfaces.

[0046] Example 2:

[0047] In order to obtain the best quality solid alternative fuel, this embodiment prepared the solid alternative fuel using the above-mentioned preparation method, and verified the effects of the gasification fine slag fraction being greater than the municipal sludge fraction, the gasification fine slag fraction being equal to the municipal sludge fraction, and the gasification fine slag fraction being less than the municipal sludge fraction on the calorific value of the final solid alternative fuel, so as to obtain the optimal component ratio.

[0048] By weight, the experimental groups are as follows:

[0049] Group A: 35 parts of gasification fine residue, 15 parts of municipal sludge, and 50 parts of citrus fruit by-products;

[0050] Group B: 25 parts of gasification fine residue, 25 parts of municipal sludge, and 50 parts of citrus fruit by-products;

[0051] Group C: 15 parts of gasification fine residue, 35 parts of municipal sludge, and 50 parts of citrus fruit by-products.

[0052] The calorific value of the solid alternative fuels prepared in the three groups was tested, and the results are shown in Table 1:

[0053] Table 1 Calorific value results of solid alternative fuels

[0054] Group Lower calorific value (MJ / kg) Group A 13.79±0.14 Group B 12.53±0.08 Group C 12.33±0.04

[0055] As shown in Table 1, the solid alternative fuel produced using the component ratio provided by Group A has the highest calorific value, reaching 13.79 MJ / kg. This means that when the proportion of gasified fine slag is greater than that of municipal sludge, the calorific value of the resulting solid alternative fuel is increased. However, because municipal sludge, at a certain ratio, can provide an appropriate amount of organic matter, it helps improve the fuel's combustion characteristics and reduce pollutant generation. If the amount of municipal sludge is too low, the fuel's combustion stability decreases, the ash content increases, and the adverse environmental impact increases. Therefore, the component ratio of Group A is used here as the optimal ratio for producing the highest-quality solid alternative fuel.

[0056] Example 3:

[0057] In order to obtain the best quality solid alternative fuel, this example used the above-mentioned preparation method to prepare the solid alternative fuel as an experimental process. The temperature, pressure, holding time and compression rate were used as variables. The following experiments were conducted to obtain the optimal preparation process parameters:

[0058] (1) Experimental variables for molding strips with different temperatures, pressures, holding times, and compression rates are set. The values ​​of each variable are shown in Table 2:

[0059] Table 2. Identification, parameter range and coding value table of experimental variables

[0060] Experimental variables / levels -1 0 1 Pressure (MPa) 40 70 100 Temperature (℃) 80 120 160 Compression speed (mm / s) 10 20 30 Holding time (s) 200 300 400

[0061] (2) Under different molding temperature, pressure, compression rate and holding time conditions, the final solid alternative fuel was air-dried indoors for 5 minutes, and the density, compressive strength and specific energy consumption were tested.

[0062] The density of solid alternative fuel is calculated as follows:

[0063] ρ=m / V=4m / πld 2

[0064] Where ρ is the density of the fuel (g / cm 3 ), m is the mass of the fuel (g); V is the volume of the fuel (cm 3 ); l is the length of the fuel (cm); d is the diameter of the fuel (cm).

[0065] The compressive strength of solid alternative fuels is measured using a type I electronic universal testing machine. The compressive strength is defined as the applied force divided by the projected indentation area. The calculation formula is as follows:

[0066] H=F / S

[0067] Where H is the compressive strength (N / mm 2 ); F is the maximum pressure of the pressing rod (N); S is the indentation area of ​​the pressing rod projection (mm 2 ).

[0068] The specific energy consumption of solid alternative fuel is measured by using a force sensor to measure the relationship between the pressure and displacement at the bottom of the pressing rod. The energy consumption is calculated by integration. The calculation formula is as follows: W) = ∑(Fi * Si) / m

[0069] Where Fi is pressure (N), Si is displacement (m), and m is material mass (g).

[0070] The specific experimental results are shown in Table 3 below:

[0071] Table 3 Response surface experimental design and results

[0072] serial number Temperature (℃) Pressure (MPa) Holding time (s) Compression rate (mm / s) <![CDATA[Density (g / cm 3 ).]]> <![CDATA[Compressive strength (N / cm 2 ).]]> Specific energy consumption (J / g) 1 80.00 40.00 300.00 20.00 1.01 0.13 7.58 2 160.00 40.00 300.00 20.00 1.19 0.69 6.35 3 80.00 100.00 300.00 20.00 1.15 0.44 15.32 4 160.00 100.00 300.00 20.00 1.31 1.34 13.13 5 120.00 70.00 200.00 10.00 1.18 0.94 10.71 6 120.00 70.00 400.00 10.00 1.24 1.38 10.61 7 120.00 70.00 200.00 30.00 1.22 0.74 11.01 8 120.00 70.00 400.00 30.00 1.22 0.81 11.79 9 80.00 70.00 300.00 10.00 1.11 0.35 11.11 10 160.00 70.00 300.00 10.00 1.21 0.43 9.90 11 80.00 70.00 300.00 30.00 1.07 0.22 12.60 12 160.00 70.00 300.00 30.00 1.20 0.55 10.78 13 120.00 40.00 200.00 20.00 1.17 0.68 6.17 14 120.00 100.00 200.00 20.00 1.23 0.71 12.79 15 120.00 40.00 400.00 20.00 1.16 0.57 6.41 16 120.00 100.00 400.00 20.00 1.30 1.37 13.43 17 80.00 70.00 200.00 20.00 1.10 0.31 11.44 18 160.00 70.00 200.00 20.00 1.22 0.73 10.04 19 80.00 70.00 400.00 20.00 1.13 0.31 11.73 20 160.00 70.00 400.00 20.00 1.25 0.98 10.29 21 120.00 40.00 300.00 10.00 1.15 0.51 6.53 22 120.00 100.00 300.00 10.00 1.29 1.06 13.91 23 120.00 40.00 300.00 30.00 1.13 0.61 7.03 24 120.00 100.00 300.00 30.00 1.29 1.25 14.21 25 120.00 70.00 300.00 20.00 1.25 1.16 9.97 26 120.00 70.00 300.00 20.00 1.27 1.17 10.19 27 120.00 70.00 300.00 20.00 1.24 0.62 10.76 28 120.00 70.00 300.00 20.00 1.16 0.53 12.19 29 120.00 70.00 300.00 20.00 1.21 0.75 10.52

[0073] The experimental results of the density of the solid alternative fuels prepared under different molding temperatures, pressures, compression rates, and holding times are shown in Table 4:

[0074] Table 4 Density results under different parameters

[0075] Sources of variance Sum of Squares of Deviations mean square F-number P-value Model 0.13 <![CDATA[9.44×10 -3 ]]> 11.07 <0.0001 significant temperature 0.057 0.057 66.47 <0.0001 pressure 0.047 0.047 54.91 <0.0001 Holding time <![CDATA[2.473×10 -3 ]]> <![CDATA[2.47×10 -3 ]]> 2.90 0.1108 Compression rate <![CDATA[1.069×10 -4 ]]> <![CDATA[1.00×10 -4 ]]> 0.13 0.7287 Lack of Fit <![CDATA[4.483×10 -3 ]]> <![CDATA[4.48×10 -4 ]]> 0.24 0.9694 Not significant

[0076] As shown in Table 4, the influence of each parameter on the density of the briquetting fuel is, from large to small, temperature, pressure, holding time and compression rate.

[0077] The experimental results of the compressive strength of the fuels produced under different molding temperatures, pressures, compression rates, and holding times are shown in Table 5:

[0078] Table 5 Compressive strength results under different parameters

[0079] Sources of variance Sum of Squares of Deviations mean square F-number P-value Model 2.70 0.19 3.21 0.0185 significant temperature 0.73 0.73 12.11 0.0037 pressure 0.74 0.74 12.26 0.0035 Holding time 0.14 0.14 2.40 0.1437 Compression rate 0.020 0.020 0.33 0.5735 Lack of Fit 0.47 0.047 0.51 0.8203 Not significant

[0080] As shown in Table 5, the influence of various parameters on the compressive strength of the briquette fuel is, from large to small, pressure, temperature, holding time and compression rate.

[0081] The experimental results of fuel specific energy consumption under different molding temperature, pressure, compression rate and holding time are as follows:

[0082] Table 6 Specific energy consumption results under different parameters

[0083] Sources of variance Sum of Squares of Deviations mean square F-number P-value Model 166.79 11.91 39.46 <0.0001 significant temperature 7.22 7.22 23.91 0.0002 pressure 152.11 152.11 503.74 <0.0001 Holding time 0.37 0.37 1.22 0.2889 Compression rate 1.79 1.79 5.93 0.0288 Lack of Fit 1.19 0.12 0.16 0.9918 Not significant

[0084] As shown in Table 6, the influence of each parameter on the specific energy consumption of molding fuel is, from large to small, pressure, temperature, compression rate and holding time.

[0085] Design Expert 8 was used to optimize the process parameters based on this optimization condition. The optimal process parameters were calculated to be: molding pressure of 74.17 MPa, molding temperature of 141.44°C, holding time of 400 s, and compression rate of 11.66 mm / s.

[0086] The solid alternative fuel prepared under the optimal process parameters has a molding density of 1.28 g / cm 3 , compressive strength is 1.22 N / cm 2 , the specific energy consumption is 10.65 J / g.

[0087] Example 4:

[0088] In this embodiment, a combustion experiment is conducted on the prepared solid alternative fuel using a thermogravimetric analyzer.

[0089] In this example, a simultaneous thermal analyzer (STAA449F5, Netzsch, SelB, Germany) was used to analyze the combustion properties of the fuel. Before the experiment, approximately 25 ± 0.2 mg of sample was weighed using a digital balance with an accuracy of 0.00001 g. The experimental conditions were set as a heating rate of 20°C / min, an air atmosphere at a flow rate of 20 mL / min, a temperature range of 30°C to 1000°C, and nitrogen as the shielding gas.

[0090] The obtained TG and DTG curves are shown in the attached Figure 3 As shown, the fuel combustion process can be divided into three main stages:

[0091] (1) The first stage (50-280℃): This stage mainly involves the release of water and low-boiling-point substances.

[0092] (2) The second stage (280-585℃): In this stage, volatiles begin to be released and burn in large quantities. The maximum release rate of volatiles increases with increasing temperature. This phenomenon is not only attributed to the increase in temperature, but also because a loose structure is formed on the sample surface during the release of volatiles, which increases the contact area with air and accelerates the release of internal volatiles.

[0093] (3) The third stage (585-880℃): This stage mainly involves the combustion of fixed carbon and non-volatile substances, and the mass loss at this time is minimal.

[0094] Table 7 shows the combustion characteristic parameters of the composite rod sample, derived from the TG and DTG curves. Ti represents the combustion initiation temperature and is an important indicator for evaluating the fuel's ignition ability. Tb is the combustion termination temperature, reflecting the temperature range within which the sample's combustion reaction ends. This helps assess the material's complete combustion and the properties of its residue. The flammability index (S) is a key parameter for evaluating a material's combustion performance. A higher S value indicates a better material's combustion performance.

[0095] Table 7 Combustion characteristic parameters

[0096] <![CDATA[T i (℃)]]> <![CDATA[T m (℃)]]> <![CDATA[T b (℃)]]> <![CDATA[DTG max (% / min)]]> <![CDATA[DTG mean (% / min)]]> <![CDATA[S×10 -7 (% / ℃ 3 / min 2 )]]> 280.6 822.1 881.9 6.57 1.84 17.47

[0097] According to Table 7, the solid alternative fuel has a lower ignition temperature (280.6℃) and a higher burnout temperature (881.9℃), and has an excellent flammability index (S) of 17.47% / ℃. 3 / min 2 , indicating that the fuel has excellent combustion performance.

[0098] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for preparing solid alternative fuel based on gasified fine slag, characterized in that: The following steps are involved: (1) Pre-treating the raw materials, wherein the raw materials include 35 parts by weight of gasification fine residue, 15 parts by weight of municipal sludge, and 50 parts by weight of citrus fruit by-products; the specific process of pre-treating the raw materials is as follows: reducing the moisture content of the gasification fine residue filter cake, municipal sludge, and citrus fruit by-products to less than 10% by natural air drying or drying, and then crushing them with a crusher and passing them through a 100-mesh sieve to obtain pre-treated gasification fine residue powder, municipal sludge powder, and citrus fruit by-product powder; (2) Mixing the pretreated raw materials; (3) The mixed raw materials are added to a granulation device and extruded into a cylindrical solid alternative fuel having a smooth surface, wherein the extrusion parameters of the cylindrical solid alternative fuel having a smooth surface meet at least one of the following conditions: a. Extrusion pressure is 74.17MPa; b. Extrusion temperature is 141.44℃; c. Holding time is 400 s; d. Compression rate is 11.66 mm / s; The molding density of the solid alternative fuel is 1.28 g / cm 3 , compressive strength is 1.22 N / cm 2 and a specific energy consumption of 10.65 J / g.

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