Adjustable variable-frequency rapid pyrolysis method for capturing microwave hot spots by organic solid waste source components

Abstract

The invention relates to an adjustable and controllable variable-frequency rapid pyrolysis method for capturing microwave hot spots by organic solid waste source components, and belongs to the technical field of organic solid waste energy recovery. In order to solve the technical problems of high microwave frequency input, low heating rate, non-uniform heating and the like caused by direct microwave pyrolysis of solid wastes in the engineering field, the invention provides a method for carrying out pyrolysis by classifying and extracting solid waste components and applying microwave frequencies of different wave bands and accelerating a reaction by moisture. Under the frequency of 1.5 GHz-4. 5GHz, the heating rates of the protein, the polysaccharide and the humic acid are in positive correlation, and the wave absorbing capacity of the protein is obviously higher than that of the polysaccharide and the humic acid; different moisture further induces water-gas exchange reaction, and generation of hydrogen containing protein, polysaccharide and humic acid components is effectively promoted. And finally, respectively providing parameter setting schemes of microwave pyrolysis scenes of solid wastes rich in protein components and polysaccharide components. The invention provides a promising strategy for energy conservation, consumption reduction and energy recovery of an organic solid waste microwave pyrolysis technology.

Description

Technical Field

[0001] The invention relates to a pyrolysis method and belongs to the technical field of organic solid waste energy recovery. Background Art

[0002] As a new generation of organic solid waste resource disposal technology that has attracted widespread attention in recent years, pyrolysis has significant advantages such as efficient removal of difficult-to-degrade substances, low harm from by-products, high product resource utilization value, and low operating costs. However, traditional pyrolysis technology uses electric heating to heat up the solid waste from the outside to the inside, which can easily lead to technical problems such as slow heating rate and high energy consumption. Microwave thermal decomposition coupling technology has been proven to have significant advantages over traditional pyrolysis. With its unique rapid heating mechanism, microwaves can quickly and selectively heat up the solid waste from the inside to the outside. It has the advantages of short time, fast speed, and low heat loss. It is recognized as one of the most effective solid waste treatment technologies.

[0003] Sludge is a complex system composed of multiple media components, and its organic composition is the key factor in achieving stable operation of microwave pyrolysis. Sludge is mainly composed of 7% to 19% carbohydrates, 25% to 62% protein, 8% to 29% humus and <3.5% DNA. Due to the microwave absorption capacity of different components, there are significant differences in the heat conduction rates of different components during the pyrolysis process. Crucially, the non-uniform distribution of different dielectric loss components inside the sludge makes it difficult to capture microwave hotspots, which has become a current problem facing microwave pyrolysis technology.

[0004] Therefore, it is urgent to propose an adjustable variable frequency rapid pyrolysis method for capturing microwave hotspots of organic solid waste source components to solve the above technical problems. Summary of the invention

[0005] In order to solve the above problems, an adjustable variable frequency rapid pyrolysis method for capturing microwave hotspots of organic solid waste source components is provided. In order to ensure efficient pyrolysis of solid waste, the current common method of directly pyrolyzing solid waste has problems such as high microwave frequency setting, slow heating rate, uneven heating, etc., thereby increasing energy consumption input. The present invention proposes to classify and extract the solid waste components for pre-treatment, and select microwave frequencies of different bands based on the different absorption capabilities of the solid waste components, which is conducive to reducing energy consumption and accelerating pyrolysis. A brief overview of the present invention is given below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to determine the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0006] The technical solution of the present invention:

[0007] The method for rapid pyrolysis of organic solid waste source components by controlling microwave hot spots with adjustable frequency conversion comprises the following steps:

[0008] Step 1: Collect samples;

[0009] Step 2: separation and extraction of sample components;

[0010] Step 3: Preparation of samples with different water contents;

[0011] Step 4: Microwave pyrolysis.

[0012] Preferably: in step 1, the sample source is a component containing a microwave absorption source, including sludge, oil sludge, pharmaceutical waste residue, saline-alkali soil and / or biomass.

[0013] Preferably: in step 2, the separated and extracted sample components include protein, polysaccharide and humic acid.

[0014] Preferably: Step 2 comprises the following steps:

[0015] The sample solution is subjected to certain temperature and pH treatments, and the supernatant is concentrated;

[0016] adding anhydrous ethanol to the supernatant and allowing the mixture to stand for a period of time at a certain temperature; centrifuging the obtained mixture to obtain a precipitate;

[0017] Redissolve the precipitate in deionized water; add 100% w / v trichloroacetic acid solution to the re-dissolved solution to make the concentration of the 100% w / v trichloroacetic acid solution reach the set concentration, and let it stand;

[0018] The resulting precipitate was washed with acetone to remove residual trichloroacetic acid and obtain crude protein;

[0019] The ethanol precipitation procedure was repeated on the supernatant to obtain crude polysaccharides;

[0020] Extract humic acid.

[0021] Preferably: in step 2, the sludge with a solid content of 4-6 wt% is treated at 85°C-87°C and pH 12 for 5-5.4 hours, and then the supernatant is concentrated to 1 / 4 of its original volume;

[0022] Anhydrous ethanol in a volume three times that of the concentrated supernatant was added and allowed to stand at 4°C–5°C for 12 h. The obtained mixture was centrifuged at 10,000 g for 10–15 min to obtain a precipitate, which was then redissolved in deionized water;

[0023] Set the concentration to 13%–15% and place at 4°C–5°C overnight;

[0024] Wash the resulting precipitate three more times with acetone;

[0025] The extraction process of humic acid used a modified recommended method described in the International Humic Substances Society.

[0026] Preferably: in step three, the sample, protein, polysaccharide, and humic acid are mixed with deionized water in different proportions to prepare samples containing different amounts of water, and the samples are placed in a constant temperature water bath or an air oscillator and rotated and mixed at room temperature.

[0027] Preferably: in step 4, samples with different water contents are placed in quartz reactors in a microwave chamber respectively; the temperature is increased from room temperature to -1000°C; and microwave irradiation is performed on the samples with different water contents, emitting electromagnetic waves with a frequency between 300 MHz and 3000 GHz.

[0028] Preferably: the adjustable frequency variable rapid pyrolysis method of source component capturing microwave hot spots is applied to the disposal of organic solid waste.

[0029] Preferred: different types of organic solid waste have different proportions of main components; based on the results of this experiment, organic solid wastes such as microalgae and sludge are rich in protein components, and the microwave frequency required in this scenario is relatively high; and when pyrolyzing straw and stalk solid wastes rich in polysaccharides, the microwave frequency setting can be considered to be reduced to 1.5 GHz.

[0030] The present invention has the following beneficial effects:

[0031] The present invention establishes a microwave pyrolysis technology route for treating different components of sludge in different paths, providing an effective strategy for solving the problems of microwave hotspot capture, high energy input, and achieving rapid pyrolysis;

[0032] The present invention helps to improve the heat absorption potential of the solid waste pyrolysis process through different water contents, reduces costs, increases efficiency, and saves energy and protects the environment;

[0033] The present invention creatively proposes a strategy for combining microwave pyrolysis of solid waste with different water contents and organic component distribution paths, which provides important theoretical and practical guidance for the engineering application of microwave pyrolysis technology in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic diagram of a microwave pyrolysis apparatus.

[0035] Figure 2 This is a graph of the heating rates of protein, polysaccharide and humic acid components at different microwave frequencies.

[0036] Figure 3 This is a graph showing the hydrogen yield of protein, polysaccharide and humic acid when different amounts of water are added.

[0037] In the figure, 1 is a microwave chamber, 2 is a quartz reactor, 3 is a waveguide, 4 is a magnetron, 5 is a PC fuzzy logic algorithm (computer), 6 is a power regulator, 7 is an infrared thermometer, 8 is a gas flow meter, 9 is a tar product collection device, and 10 is a gas collection device. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0039] Specific implementation method 1: Combination Figure 1-3 The present embodiment is described. The adjustable frequency variable rapid pyrolysis method for capturing microwave hotspots of organic solid waste source components in the present embodiment comprises the following steps:

[0040] Step 1: Collect samples (organic solid waste);

[0041] In step 1, the sample collection source is a component containing a microwave absorption source, including sewage sludge, oil sludge, pharmaceutical waste residue, saline-alkali soil and / or biomass;

[0042] Step 2: Separation and extraction of protein, polysaccharide and humic acid components in the sample;

[0043] In step 2, the sample components separated and extracted include protein, polysaccharide and humic acid; the steps include:

[0044] Step 2.1: The sample solution is subjected to a certain temperature and pH treatment, and the supernatant is concentrated;

[0045] In step 2.1, sludge with a solid content of 4–6 wt% was treated at 85°C–87°C and pH 12 for 5–5.4 h, and the supernatant was then concentrated to 1 / 4 of its original volume;

[0046] Step 2.2: adding anhydrous ethanol to the supernatant, and standing at a certain temperature for a period of time; centrifuging the obtained mixture to obtain a precipitate;

[0047] In step 2.2, anhydrous ethanol was added in a volume three times that of the concentrated supernatant, and the mixture was allowed to stand at 4°C–5°C for 12 h. The obtained mixture was centrifuged at 10,000 g for 10–15 min to obtain a precipitate, which was then redissolved in deionized water. This step was intended to exclude the influence of humic acid on the subsequent protein precipitation process.

[0048] Step 2.3: Redissolve the precipitate in deionized water; add 100% w / v trichloroacetic acid solution to the re-dissolved solution to make the concentration of the 100% w / v trichloroacetic acid solution reach the set concentration, and let it stand;

[0049] In step 2.3, the concentration was set to 13%–15%, and the culture was allowed to stand at 4°C–5°C in the dark for 12 hours;

[0050] Step 2.4: washing the obtained precipitate with acetone to remove the residual trichloroacetic acid to obtain the crude protein;

[0051] In step 2.4, the obtained precipitate is washed with acetone three or more times;

[0052] Step 2.5: Repeat the ethanol precipitation procedure (step 2.2) on the supernatant to obtain crude polysaccharides;

[0053] Step 2.6: Extracting humic acid; the present invention separates and extracts the components step by step, and the operation is reasonable and simple;

[0054] In step 2.6, the extraction process of humic acid adopts the improved recommended method described in the International Humic Substances Society; for example: under a nitrogen atmosphere, 5 mol / L HCl solution is slowly added to the supernatant of the sludge treated with hot alkali until the pH value is lower than 2; after standing for 12 hours, solid-liquid separation is performed, and the precipitate is rinsed with deionized water until Cl- is not detected in the eluent, thereby obtaining humic acid. The steps of the present invention are combined with reasonable parameter settings to further reduce costs, improve efficiency, and each component has high purity;

[0055] Step 3: Preparation of samples with different water contents;

[0056] In step 3, the dry sludge sample, protein, polysaccharide, and humic acid components are mixed with deionized water in different proportions to prepare samples containing different amounts of water, and finally placed in a constant temperature water bath or an air oscillator and rotated and mixed at room temperature;

[0057] Step 4: microwave pyrolysis test;

[0058] In step 4, samples with different water contents (0.25-0.75 mL, below 5 wt%) are placed in a quartz reactor 2 in a microwave chamber 1; an inert gas is introduced into the quartz reactor 2, and the gas flow rate is monitored by a gas flow meter 8, and the heating rate is adjusted by a power regulator 6, and the temperature is raised from room temperature to 1000° C.; after reaching the set temperature by an infrared thermometer, microwave radiation is applied to the samples with different water contents through a waveguide, and the power regulator 6 is used to adjust the emission frequency of electromagnetic waves between 300 MHz and 3000 GHz to achieve variable frequency controlled pyrolysis; the generated gas is treated by a tar product collection device 9 and a gas collection device 10 for environmental protection;

[0059] In order to eliminate the negative impact that the conversion of volatile substances may be significantly interfered by the residence time, the microwave irradiation time of the sample solution was controlled at 8-9 minutes. According to experimental verification, there was almost no volatile matter in the solid residue after 8 minutes, which improved the efficiency and ensured the prevention of interference while reducing energy consumption.

[0060] The method is applied to the disposal of organic solid waste, with high efficiency and low energy consumption;

[0061] Generally, different types of organic solid waste have different proportions of main components. Based on the results of this experiment, organic solid wastes such as microalgae and sludge are rich in protein, and the microwave frequency required in this scenario is relatively high. When pyrolyzing solid wastes such as straw and stalks rich in polysaccharides, the microwave frequency setting can be considered to be reduced to 1.5GHz.

[0062] Establishing a microwave pyrolysis technology route for the treatment of different components of sludge is an effective strategy to solve the problem of microwave hotspot capture and achieve rapid pyrolysis. High-water content solid waste helps to increase the heat absorption potential of the solid waste pyrolysis process due to its high specific heat capacity and latent heat of evaporation. Therefore, the microwave pyrolysis strategy of solid waste based on different moisture contents and organic component treatment paths provides important theoretical and practical guidance for the future engineering application of microwave pyrolysis technology.

[0063] Embodiment 1:

[0064] Before microwave heating, the sludge samples and sludge components (ingredients) were added to the microwave cavity in batches; after the experiment, the solid residue was recovered; in order to maintain a strict inert atmosphere, high-purity argon was continuously injected into the pyrolysis system at a flow rate of 10L / min for 20 minutes to exhaust oxygen; the microwave generator was turned off after reaching the specified reaction time; high-purity argon was re-injected into the pyrolysis system for 20 minutes to remove residual gas;

[0065] The protein, polysaccharide and humic acid samples extracted from the sludge samples were vacuum freeze-dried at -55°C for 24 hours to obtain dry powder samples; then, 1g of protein, polysaccharide and humic acid powders were weighed respectively for batch microwave pyrolysis experiments, and the microwave frequency ranged from 1GHz to 5GHz; the temperature in the microwave cavity was increased from room temperature to 700°C, and the average heating rate was recorded; when the temperature in the microwave pyrolysis cavity reached the specified temperature, it was maintained for 20 minutes, and tar and gas products were collected simultaneously; finally, when the temperature in the microwave cavity dropped to room temperature, the solid residue, i.e., biochar, was taken out;

[0066] The results obtained in Example 1 show that microwave frequency is positively correlated with the pyrolysis heating rates of protein, polysaccharide and humic acid, indicating that the three main components in sludge have absorption characteristics for microwaves; among them, protein exhibits the strongest microwave absorption capacity, followed by polysaccharide and humic acid; the above results may be attributed to the polar properties of protein; relevant reports show that microwaves easily absorb polar molecules; in addition, compared with 1.5 GHz, the heating rates of protein, polysaccharide and humic acid at 3 GHz increase by 49.1%, 44.6% and 51.7%, respectively, and at 4.5 GHz increase by 63.5%, 67.3% and 74.9%, respectively; from Figure 3 It was found that the increase in hydrogen yield from microwave frequency from 1.5GHz to 3GHz was higher than that from 3GHz to 4.5GHz. Based on energy consumption and maximum product yield, 3GHz is the optimal microwave frequency. At 1.5GHz-4.5GHz, the heating rates of protein, polysaccharide, and humic acid are positively correlated, and the protein absorption capacity is significantly higher than that of polysaccharide and humic acid. Different moisture content further induces water-gas exchange reactions, effectively promoting the production of hydrogen in protein, polysaccharide, and humic acid components. Finally, parameter setting schemes for microwave pyrolysis scenarios of solid waste rich in protein components and polysaccharide components are proposed respectively. The present invention provides a promising strategy for energy saving and consumption reduction and energy recovery in microwave pyrolysis technology of organic solid waste.

[0067] Generally, different types of organic solid waste have different proportions of main components. Based on the results of this experiment, organic solid wastes such as microalgae and sludge are rich in protein, and the required microwave frequency in this scenario is relatively high. When pyrolyzing solid wastes such as straw and stalks rich in polysaccharides, the microwave frequency setting can be considered to be reduced to 1.5 GHz.

[0068] Embodiment 2:

[0069] Before microwave heating, the sludge samples and sludge components (ingredients) were added to the microwave cavity in batches; after the experiment, the solid residue was recovered; in order to maintain a strict inert atmosphere, high-purity argon was continuously injected into the pyrolysis system at a flow rate of 10L / min for 20 minutes to exhaust oxygen; the microwave generator was turned off after reaching the specified reaction time; high-purity argon was re-injected into the pyrolysis system for 20 minutes to remove residual gas;

[0070] Each batch of tests connects gas and tar sample collection pipelines; volatile substances pass through a dichloromethane condenser placed in an ice bath; the mixed gas is then transported from the tar collector to a gas collection bag; tar is collected from the condenser by evaporating the dichloromethane solvent at 60°C for 24 hours; the residual coal char is stored in an airtight container; the yield of char and tar is calculated based on the weight of each component, and the gas yield is determined by the difference;

[0071] Ultrapure water was taken, and 0.25, 0.5, and 0.75 mL of ultrapure water were added to the dried protein powder samples, respectively, and microwave pyrolysis tests were performed in batches; the above operation was repeated for polysaccharides and humic acid; wherein 3 GHz in implementation case 1 was used as the microwave frequency condition for this test; finally, the gas was collected for analysis, and the gas results were recorded as the volume percentage (%) of a single gas component in the total gas output;

[0072] The results obtained in Example 2 show that the hydrogen yield generated by microwave pyrolysis of protein is close to that of polysaccharide, while the hydrogen yield obtained by humic acid is the lowest; this may be attributed to the fact that the structures of protein and polysaccharide are easier to decompose, while humic acid is a difficult-to-degrade substance;

[0073] In addition, hydrogen generation originates from the water-gas exchange reaction Therefore, as the water content increases, the hydrogen production rates of protein, polysaccharide and humic acid components by microwave pyrolysis all increase.

[0074] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A controllable variable frequency rapid pyrolysis method for capturing microwave hot spots of organic solid waste source components, characterized by: The following steps are involved: Step 1: Collect samples; Step 2: separation and extraction of sample components; Step 3: Preparation of samples with different water contents; Step 4: Microwave pyrolysis.

2. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 1, characterized in that: In step 1, the sample source is a component containing a microwave absorption source, including sewage sludge, oil sludge, pharmaceutical waste residue, saline-alkali soil and / or biomass.

3. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 1 or 2, characterized in that: In step 2, the separated and extracted sample components include protein, polysaccharide and humic acid.

4. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 3, characterized in that: Step 2 includes the following steps: The sample solution is subjected to certain temperature and pH treatments, and the supernatant is concentrated; adding anhydrous ethanol to the supernatant and allowing the mixture to stand for a period of time at a certain temperature; centrifuging the obtained mixture to obtain a precipitate; Redissolve the precipitate in deionized water; add 100% w / v trichloroacetic acid solution to the re-dissolved solution to make the concentration of the 100% w / v trichloroacetic acid solution reach the set concentration, and let it stand; The resulting precipitate was washed with acetone to remove residual trichloroacetic acid and obtain crude protein; The ethanol precipitation procedure was repeated on the supernatant to obtain crude polysaccharides; Extract humic acid.

5. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 4, characterized in that: In step 2, sludge with a solid content of 4–6 wt% was treated at 85°C–87°C and pH 12 for 5–5.4 h, and the supernatant was concentrated to 1 / 4 of its original volume; Anhydrous ethanol in a volume three times that of the concentrated supernatant was added and allowed to stand at 4°C–5°C for 12 h. The obtained mixture was centrifuged at 10,000 g for 10–15 min to obtain a precipitate, which was then redissolved in deionized water; Set the concentration to 13%–15% and place at 4°C–5°C overnight; Wash the resulting precipitate three more times with acetone; The extraction process of humic acid used a modified recommended method described in the International Humic Substances Society.

6. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 5, characterized in that: In step 3, the sample, protein, polysaccharide, and humic acid are mixed with deionized water in different proportions to prepare samples with different water contents, ranging from 0.25 to 0.75 mL, and placed in a constant temperature water bath or air oscillator, and rotated and mixed at room temperature; As the water content increases, the hydrogen production rate of protein, polysaccharide and humic acid components by microwave pyrolysis increases.

7. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 6, characterized in that: In step 4, samples with different water contents are placed in a quartz reactor (2) in a microwave chamber (1); the microwave frequency ranges from 1 GHz to 5 GHz, and the temperature increases from room temperature to 1000°C. The microwave frequency is positively correlated with the pyrolysis heating rate of protein, polysaccharide, and humic acid, indicating that the three main components in the sludge have absorption characteristics for microwaves.

8. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 7, characterized in that: Used for the disposal of organic solid waste.

9. The method for rapid pyrolysis of organic solid waste source components for capturing microwave hot spots with adjustable frequency conversion according to claim 8, characterized in that: Different types of organic solid waste have different proportions of main components. Based on the results of this experiment, organic solid wastes such as microalgae and sludge are rich in protein, and the required microwave frequency in this scenario is relatively high. When pyrolyzing straw and stalk solid wastes rich in polysaccharides, the microwave frequency setting can be considered to be reduced to 1.5 GHz.

Images