Solid alternative fuel based on gasified fine slag and preparation method thereof

Abstract

The invention relates to the technical field of solid waste resource utilization, and particularly discloses a solid alternative fuel based on gasification fine slag, the solid alternative fuel comprises, by weight, 10-40 parts of gasification fine slag, 10-40 parts of municipal sludge, and 30-70 parts of citrus fruit by-products, the molding density of the solid alternative fuel is 1.28 g / cm < 3 >, the compressive strength is 1.22 N / cm < 2 >, and the specific energy consumption is 10.65 J / g. The specific preparation process comprises the following steps: 1) respectively pretreating the raw materials; (2) mixing the pretreated raw materials; and (3) adding the mixed raw materials into granulation equipment, and extruding into the cylindrical solid alternative fuel with a smooth surface. The solid alternative fuel is prepared by adding the municipal sludge and the biomass on the basis of the gasified fine slag, the defect of low combustion heat value of the gasified fine slag is overcome, the ash content can be reduced, the solid alternative fuel meets the condition of resource utilization, the solid alternative fuel has high density and compressive strength, the solid alternative fuel can be conveniently transported and stored as a fuel product, and the solid alternative fuel is suitable for industrial production. And a new technical thought and direction are provided for the utilization of the gasified 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 fine slag is a solid waste generated during the coal gasification process. The harm of gasification fine slag is mainly reflected in its pollution to the environment and waste of land resources. With the development of coal gasification technology, the stockpile of gasification fine slag has been increasing, causing serious environmental problems. Coal gasification slag contains incompletely burned carbon residues, metal oxide minerals, etc. If these components are not properly handled, they will pollute the environment. The combustion disposal of coal gasification slag is an effective large-scale treatment method. Gasification fine slag has a high carbon content, a large specific surface area, and a developed pore structure. When burned alone, it shows low calorific value, incomplete combustion, and high ash content. The shortcomings make the gasification fine slag unable to be used directly as fuel. In addition, general boilers cannot burn gasification fine slag filter cakes with too small particle size. Therefore, mixing gasification fine slag with raw coal in a certain proportion has become its main disposal method. However, the amount of gasification fine slag that can be processed each time is small, and the gasification fine slag produced is far more than the recycled gasification fine slag, which leads to more and more gasification fine slag and the inability to make full use of gasification fine 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 scheme: a solid alternative fuel based on gasified fine slag, including 35 parts of gasified fine slag, 15 parts of urban 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 the specific energy consumption is 10.65 J / g.

[0006] The working principle of this technical solution is that the addition of sludge and citrus peel improves the low calorific value of coal gasification fine slag when burned alone, while the low ash content improves the high slagging potential of citrus peel when burned alone, which can meet the resource utilization. This solid alternative fuel has the advantages of high calorific value, high density, strong wear resistance (high compressive strength and wear resistance), low energy consumption and high combustion potential, which facilitates the production, transportation and use of fuel. The invention of this mixed solid alternative fuel provides a new idea for the disposal of gasification fine slag, sludge and peel biomass, and realizes the comprehensive disposal of solid waste.

[0007] Municipal sludge refers to the solid waste generated by sewage treatment plants in the process of treating domestic sewage and industrial wastewater during the urbanization process. In the rapid wave of urbanization and industrialization, the problem of excess sludge production has become a key obstacle to achieving sustainable social development. At present, the proportion of incineration treatment in the field of sludge disposal in China has reached a fairly high level. Sludge is rich in organic matter, usually accounting for 40% to 70% of the total weight. These organic matters not only have a high calorific value (high calorific value on a dry basis is 8 to 15 MJ / kg), but also indicate its potential in energy conversion. Although the practice of converting sludge into derivative fuels is in its infancy, its proportion in the total amount of sludge incineration treatment is increasing year by year, and has now reached about 10%. Taking these factors into consideration, it is expected that in the future, sludge treatment will increasingly adopt the method of converting sludge into pelletized fuel, not only because it is more economically sustainable, but also because it can better meet the needs of environmental protection and policy orientation.

[0008] Citrus peel biomass refers to biomass materials converted by physical, chemical or biotechnological means using the peels, residues and other by-products of citrus fruits as raw materials. In recent years, biomass energy has become an important part of today's new energy due to its renewable, environmentally friendly, widely distributed and high-yield advantages. Solid alternative fuels are pressed and formed by granulation equipment and have higher density and combustion stability. These technologies make it possible to convert solid waste into energy, which can not only effectively reduce the volume of waste, reduce pollutant emissions, and alleviate environmental pressure, but also be used as clean energy for heating, power generation and other fields, helping to reduce dependence on fossil fuels and promote the green transformation of the energy structure.

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

[0010] In order to better realize the present invention, further, the moisture content of the gasified fine slag, urban 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 less than 100 meshes.

[0012] In order to better realize 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 by-product of citrus fruit 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-treating the raw materials respectively;

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

[0017] (3) The mixed raw materials are added to a granulation device and extruded into a cylindrical solid alternative fuel with a smooth surface.

[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. The holding time is 200s to 400s;

[0022] d. The compression rate is 10mm / s~30mm / 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°C;

[0026] c. Holding time is 400s.

[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, municipal sludge, and citrus fruit by-products to less than 10% by natural air drying or drying, and then crushed by a crusher and passed through a 100-mesh sieve to obtain pretreated gasification fine residue powder, municipal 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 prepare a solid alternative fuel, which 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, thus providing 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 relatively 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 there is no need to add additional chemical agents such as treatment agents, adhesives and combustion aids, thereby realizing resource utilization and 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 from 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 gasification 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 clearly understood, the present invention is further described in detail in conjunction with the following embodiments, but the embodiments of the present invention are not limited thereto. Without departing from the above-mentioned technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the field, which should all 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] Embodiment 1:

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

[0040] The water content of the gasification fine residue, urban sludge and citrus fruit byproducts is less than 10%, and the gasification fine residue, urban sludge and citrus fruit byproducts are all powders with a particle size 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 respectively; the pre-treating process of the raw materials respectively comprises reducing the moisture content of the gasification fine residue filter cake, municipal sludge, and citrus fruit byproduct to less than 10% by natural air drying or drying, and then crushing them by a crusher and passing them through a 100-mesh sieve to obtain pre-treated gasification fine residue powder, municipal sludge powder, and citrus fruit byproduct powder;

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

[0045] (3) The mixed raw materials are added to a granulation device and extruded into a cylindrical solid alternative fuel with a smooth surface.

[0046] Embodiment 2:

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

[0048] The experimental groups were as follows by weight:

[0049] Group A: 35 parts of gasification fines, 15 parts of municipal sludge, and 50 parts of citrus fruit byproducts;

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

[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 three groups of prepared solid alternative fuels was tested respectively, 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] According to the contents of Table 1, the solid alternative fuel prepared by the component ratio provided by Group A has the highest calorific value, reaching 13.79MJ / kg. That is, when the amount of gasified fine slag is greater than that of urban sludge, it helps to improve the calorific value of the prepared solid alternative fuel. However, since urban sludge can provide an appropriate amount of organic matter at a certain ratio, it helps to improve the combustion characteristics of the fuel and reduce the generation of pollutants. If the content of urban sludge is too little, it will lead to a decrease in the combustion stability of the fuel, an increase in the ash content, and an increase in the adverse impact on the environment. Therefore, the component ratio of Group A is used here as the optimal ratio for obtaining the best quality solid alternative fuel.

[0056] Embodiment 3:

[0057] In order to obtain the best quality solid alternative fuel, this example uses the above preparation method to prepare the solid alternative fuel as an experimental process, and uses temperature, pressure, holding time and compression rate as variables to conduct the following experiments to obtain the best preparation process parameters:

[0058] (1) Experimental variables of different temperature, pressure, holding time and compression rate are set. The values ​​of each variable are shown in Table 2:

[0059] Table 2. Identification, parameter range and coding value table of test 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 temperatures, pressures, compression rates, and holding times, 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), and d is the diameter of the fuel (cm).

[0065] The compressive strength of solid alternative fuels is measured using an electronic universal testing machine. The compressive strength is defined as the 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 force sensor to measure the relationship curve between pressure and displacement at the bottom of the pressing rod, and 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]

[0073]

[0074] The density test results of the solid alternative fuels prepared under different molding temperatures, pressures, compression rates and holding times are shown in Table 4:

[0075] Table 4 Density results under different parameters

[0076] 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

[0077] It can be seen from Table 4 that the influence of each parameter on the density of the molding fuel is temperature, pressure, holding time and compression rate from large to small.

[0078] The test results of the compressive strength of the fuels obtained under different molding temperatures, pressures, compression rates and holding times are shown in Table 5:

[0079] Table 5 Compressive strength results under different parameters

[0080]

[0081]

[0082] It can be seen from Table 5 that the influence of each parameter on the compressive strength of the molded fuel is pressure, temperature, holding time and compression rate from large to small.

[0083] The experimental results of fuel specific energy consumption under different molding temperature, pressure, compression rate and holding time are as follows:

[0084] Table 6 Specific energy consumption results under different parameters

[0085] 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

[0086] It can be seen from Table 6 that the influence of each parameter on the specific energy consumption of molding fuel is pressure, temperature, compression rate and holding time from large to small.

[0087] Design Expert 8 was used to optimize the process parameters based on this optimization condition. The best process parameters were calculated as follows: 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.

[0088] The solid alternative fuel produced under the optimal process parameters has a molding density of 1.28g / cm 3 , compressive strength is 1.22N / cm 2 , the specific energy consumption is 10.65J / g.

[0089] Embodiment 4:

[0090] In this embodiment, a combustion experiment is conducted on the prepared solid alternative fuel using a thermogravimetric analyzer.

[0091] In this example, a synchronous thermal analyzer (STAA449F5, Netzsch, SelB, Germany) was used to analyze the combustion performance of the fuel. Before the experiment, a digital balance with an accuracy of 0.00001 g was used to weigh about 25±0.2 mg of the sample, and the experimental conditions were set as a heating rate of 20°C / min, a test atmosphere of air, a gas flow rate of 20 mL / min, a temperature range of 30°C to 1000°C, and a protective gas of nitrogen.

[0092] 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:

[0093] (1) The first stage (50-280℃): This stage mainly involves the release of water and low-boiling point substances.

[0094] (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 the increase of temperature. This phenomenon is not only attributed to the increase in temperature, but also because a loose structure is formed on the surface of the sample during the release of volatiles, which increases the contact area with the air and accelerates the release of internal volatiles.

[0095] (3) The third stage (585-880°C): This stage mainly involves the combustion of fixed carbon and non-volatile substances, and the mass loss at this time is minimal.

[0096] The combustion characteristic parameters of the composite rod sample obtained from the TG and DTG curves are shown in Table 7. Among them, Ti represents the temperature at the beginning of combustion and is an important indicator for evaluating the ignition ability of the fuel. Tb is the combustion termination temperature, which reflects the temperature range at which the sample combustion reaction ends, and helps to evaluate the completeness of the material's combustion and the nature of the residue. The flammability index (S) is a key parameter for evaluating the combustion performance of the material. The higher the S value, the better the combustion performance of the material.

[0097] Table 7 Combustion characteristic parameters

[0098] <![CDATA[T i (℃)]]> <![CDATA[T m (℃)]]> <![CDATA[T b (℃)]]> <![CDATA[DTG max (% / min)]]> <![CDATA[DTG mean (% / min)]]> <![CDATA[S×10 -7 (% / ℃ 3 / min 2 ) <!-- 7 -->]]> 280.6 822.1 881.9 6.57 1.84 17.47

[0099] According to Table 7, the solid alternative fuel has a lower ignition temperature (280.6°C) and a higher burnout temperature (881.9°C), and has an excellent flammability index (S) of 17.47% / °C. 3 / min 2 , indicating that the fuel has excellent combustion performance.

[0100] 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 present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A solid alternative fuel based on gasified fine slag, characterized in that: The solid alternative fuel comprises 10-40 parts by weight of gasification fine slag, 10-40 parts of urban sludge, and 30-70 parts of citrus fruit byproducts. 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.

2. The solid alternative fuel based on gasified fine slag according to claim 1, characterized in that: By weight, the gasification fine residue is 35 parts, the municipal sludge is 15 parts, and the by-product of citrus fruits is 50 parts.

3. A solid alternative fuel based on gasified fine slag according to claim 1 or 2, characterized in that: The water content of the gasification fine residue, urban sludge and citrus fruit by-products is less than 10%.

4. A solid alternative fuel based on gasified fine slag according to claim 1 or 2, characterized in that: The byproducts of gasification fine slag, urban sludge and citrus fruits are all powders with a particle size less than 100 meshes.

5. A solid alternative fuel based on gasified fine slag according to claim 1 or 2, characterized in that: The citrus fruit by-product includes citrus fruit peel or citrus fruit pomace.

6. The method for preparing a solid alternative fuel based on gasified fine slag according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Pre-treating the raw materials separately; (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 with a smooth surface.

7. The method for preparing a solid alternative fuel based on gasified fine slag according to claim 6, characterized in that: In 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: a. Extrusion pressure is 40Mpa~100Mpa; b. Extrusion temperature is 80℃~160℃; c. The holding time is 200s~400s; d. Compression rate is 10 mm / s~30 mm / s.

8. The method for preparing a solid alternative fuel based on gasified fine slag according to claim 7, characterized in that: In 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: a. Extrusion pressure is 74.17Mpa; b. Extrusion temperature is 141.44°C; c. Holding time is 400 s. d. The compression rate is 11.66 mm / s.

9. The method for preparing a solid alternative fuel based on gasified fine slag according to any one of claims 6 to 8, characterized in that: In the step (1), the raw materials are pretreated by reducing the moisture content of the gasification fine residue filter cake, municipal sludge, and citrus fruit byproducts 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, municipal sludge powder, and citrus fruit byproduct powder.

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