Method for preparing combustible gas and co-producing charcoal through pyrolysis / gasification of traditional Chinese medicine residues

Abstract

The invention discloses a method for preparing combustible gas and co-producing charcoal through pyrolysis / gasification of traditional Chinese medicine residues, and belongs to the technical field of solid waste recycling and energy chemical industry. The method specifically comprises the following steps: carrying out drying treatment on wet basis traditional Chinese medicine residues, and carrying out crushing and screening to obtain traditional Chinese medicine residue powder; performing microwave pyrolysis / gasification reaction on the traditional Chinese medicine residue powder in an oxygen / nitrogen atmosphere; cooperative production of combustible gas yield, components and biochar physicochemical properties is achieved, a gas product obtained after reaction is condensed and collected, combustible gas and a liquid product are obtained, and a residual solid is biochar. According to the method, synergistic conversion and directional preparation of the traditional Chinese medicine residues to high-quality combustible gas and high-added-value biochar can be achieved, a sustainable steam energy source supplement and solid waste recycling solution is provided for pharmaceutical factories, meanwhile, the development of circular economy and the achievement of pollution and carbon reduction targets are effectively promoted, and remarkable economic, environmental and social benefits are achieved.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and energy chemical technology, specifically a method for producing combustible gas and biochar by pyrolysis / gasification of traditional Chinese medicine residue. Background Technology

[0002] Traditional Chinese medicine residue, as a typical biomass waste, is mainly composed of lignocellulose. However, compared to conventional biomass such as agricultural straw, its structure is more complex. Furthermore, due to differences in the type of medicinal material and the parts used (roots, stems, leaves, flowers, and fruits), the proportions of its cellulose, hemicellulose, and lignin, as well as its ash content and the types of inorganic metals, vary significantly. This inherent complexity makes its thermochemical transformation (such as pyrolysis and gasification) difficult to predict and control.

[0003] Currently, the main methods for treating traditional Chinese medicine residue are landfilling and stockpiling, which not only occupy land but also pose environmental risks such as greenhouse gas emissions and soil pollution. Converting it into combustible gas and biochar through pyrolysis or gasification is one effective way to realize its resource utilization. However, existing technologies typically treat traditional Chinese medicine residue as a homogeneous raw material, ignoring its unique composition and structure. This leads to low conversion efficiency and unstable quality and low added value of the products (combustible gas and biochar). For example, the calorific value of the combustible gas produced by pyrolysis fluctuates greatly, and the yield is low, limiting its subsequent utilization; the resulting biochar has an underdeveloped pore structure, limiting its application value.

[0004] Therefore, there is an urgent need in this field for a new method that can achieve efficient and stable conversion of Chinese herbal medicine residues based on their component characteristics, and simultaneously improve the quality of combustible gas and biochar products. Summary of the Invention

[0005] To address or partially address the problems existing in related technologies, this invention provides a method for producing combustible gas and co-generating biochar from traditional Chinese medicine residue through pyrolysis / gasification. This method, through refined formulation of raw materials and reaction conditions, can obtain high-quality combustible gas with controllable components and high-value-added functionalized biochar. The method of this invention specifically includes the following steps: (1) The wet-based Chinese medicine residues of different medicinal parts are dried and then crushed and sieved to obtain Chinese medicine residue powder.

[0006] (2) Microwave pyrolysis / gasification of Chinese herbal medicine residue powder to obtain biochar and gas.

[0007] (3) The gas obtained in step (2) is condensed and collected to obtain non-condensable pyrolysis gas and condensed pyrolysis oil.

[0008] Preferably, the wet-based Chinese medicine residues of different medicinal parts in step (1) of the present invention include root and rhizome Chinese medicine residues and flower and leaf Chinese medicine residues, wherein the wet-based mass ratio of root and rhizome Chinese medicine residues to flower and leaf Chinese medicine residues is 1.5~4:1.

[0009] Preferably, the moisture content of the wet-based medicinal residue in step (1) of the present invention is 70%~85%. Preferably, the drying process in step (1) of the present invention is as follows: air-drying at room temperature for 24 hours, and then drying at 80~120℃ to constant weight.

[0010] Preferably, the particle size of the medicinal residue powder in step (1) of the present invention is 20-60 mesh.

[0011] Preferably, the microwave pyrolysis / gasification treatment in step (2) of the present invention is specifically as follows: pyrolysis for 30 to 60 minutes at a heating rate of 5 to 25°C / min and a temperature of 400 to 900°C, while maintaining the flow of mixed gas during the pyrolysis process.

[0012] Preferably, the mixed gas of the present invention is composed of nitrogen and oxygen, wherein oxygen accounts for 5% to 10% of the volume of the mixed gas, and the remainder is nitrogen.

[0013] Preferably, the flow rate of the mixed gas in this invention is 40~60 mL / min.

[0014] Compared with the prior art, the present invention provides a method for producing combustible gas and co-generating biochar from traditional Chinese medicine residue through pyrolysis / gasification, which has the following beneficial effects: (1) This invention combines root and leaf medicinal residues in a specific ratio and utilizes the synergistic effect of their biochemical components and inorganic minerals to effectively balance the pyrolysis pathway, so that the biochar yield, pyrolysis oil yield and combustible gas yield reach the best balance. More importantly, the synergistic catalytic effect increases the H2 / CO ratio in the combustible gas to about 2:1, making it an ideal feed gas for downstream processes such as Fischer-Tropsch synthesis and methanol synthesis, significantly improving the utilization value and economy of the gas products.

[0015] (2) The biochar prepared by this invention has a higher specific surface area, which is far superior to the biochar prepared from the residue of Chinese medicinal herbs from a single medicinal part. It can be used as a high-performance adsorbent (such as for treating wastewater and waste gas) or a functional carrier material (such as for preparing catalysts), which greatly expands the application scenarios and market value.

[0016] (3) This invention combines microwave heating with a mixed gas of a specific oxygen concentration, utilizing the characteristics of microwave heating and the exothermic effect of partial oxidation of oxygen to significantly improve pyrolysis efficiency and energy utilization. This method simultaneously converts difficult-to-treat solid waste into clean energy (combustible gas) and high-value materials (biochar and pyrolysis oil), effectively solving the common industry problem of unstable conversion process and low product quality caused by the complex source of Chinese medicine residue, and providing a reliable technical path for large-scale, high-value utilization of Chinese medicine residue. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process flow of the method of the present invention.

[0018] Figure 2 These are thermogravimetric analysis (TGA) curves of the medicinal residues of the present invention, wherein (a) is the TGA curve of the medicinal residues in Example 1, (b) is the TGA curve of the medicinal residues in Comparative Example 1, and (c) is the TGA curve of the medicinal residues in Example 2.

[0019] Figure 3 This is a graph showing biochar production under different conditions. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The root and rhizome medicinal residues used in the embodiments and comparative examples of this invention include one or more of the following: licorice, astragalus, kudzu root, and salvia miltiorrhiza; the flower and leaf medicinal residues include one or more of the following: honeysuckle, ginkgo leaves, and indigo leaves; the moisture content of the wet-based medicinal residues is approximately 70% to 85%.

[0022] Example 1 A method for producing combustible gas and co-generated biochar from traditional Chinese medicine residue by pyrolysis / gasification specifically includes the following steps: (1) The wet basis of medicinal residues of different medicinal parts were naturally air-dried at room temperature for 24 hours according to the ratio of wet basis mass of root and rhizome residues to flower and leaf residues of medicinal residues of 1.5:1, and then dried at 100℃ to constant weight. The residues were then crushed and sieved to obtain medicinal residue powder (20-60 mesh).

[0023] (2) Place the Chinese herbal medicine residue powder in a microwave pyrolysis device and heat it to 400℃ for 30 minutes at a heating rate of 5℃ / min. During the pyrolysis process, keep the mixed gas flowing (the mixed gas is composed of nitrogen and oxygen, of which oxygen accounts for 5% of the volume of the mixed gas and the remainder is nitrogen). The flow rate of the mixed gas is 40mL / min, and solid residue biochar and gas are obtained.

[0024] (3) The gas obtained in step (2) is condensed and collected to obtain non-condensable pyrolysis gas and condensed pyrolysis oil.

[0025] Example 2 A method for producing combustible gas and co-generated biochar from traditional Chinese medicine residue by pyrolysis / gasification specifically includes the following steps: (1) The wet basis Chinese medicine residues of different medicinal parts were naturally air-dried at room temperature for 24 hours according to the wet basis mass ratio of root and rhizome Chinese medicine residues to flower and leaf Chinese medicine residues of 2:1, and then dried at 80℃ to constant weight. After crushing and sieving, Chinese medicine residue powder (20-60 mesh) was obtained.

[0026] (2) Place the Chinese medicine residue powder in a microwave pyrolysis device and heat it to 700℃ for 40 minutes at a heating rate of 15℃ / min. During the pyrolysis process, keep the mixed gas flowing (the mixed gas is composed of nitrogen and oxygen, of which oxygen accounts for 7% of the volume of the mixed gas and the remainder is nitrogen). The flow rate of the mixed gas is 50mL / min, and solid residue biochar and gas are obtained.

[0027] (3) The gas obtained in step (2) is condensed and collected to obtain non-condensable pyrolysis gas and condensed pyrolysis oil.

[0028] Example 3 A method for producing combustible gas and co-generated biochar from traditional Chinese medicine residue by pyrolysis / gasification specifically includes the following steps: (1) The wet basis Chinese medicine residues of different medicinal parts were naturally air-dried at room temperature for 24 hours according to the wet basis mass ratio of root and rhizome Chinese medicine residues to flower and leaf Chinese medicine residues of 4:1, and then dried at 120℃ to constant weight. After crushing and sieving, Chinese medicine residue powder (20-60 mesh) was obtained.

[0029] (2) Place the Chinese herbal medicine residue powder in a microwave pyrolysis device and heat it to 900℃ for 60 minutes at a heating rate of 25℃ / min. During the pyrolysis process, a mixed gas is kept flowing (the mixed gas is composed of nitrogen and oxygen, of which oxygen accounts for 10% of the volume of the mixed gas and the remainder is nitrogen). The flow rate of the mixed gas is 60mL / min, and solid residue biochar and gas are obtained.

[0030] (3) The gas obtained in step (2) is condensed and collected to obtain non-condensable pyrolysis gas and condensed pyrolysis oil.

[0031] Comparative Example 1 The difference between this comparative example and Example 1 is that only root and rhizome Chinese medicine residues were used, and no raw material compatibility was performed. All other conditions are the same as in Example 1.

[0032] Comparative Example 2 The difference between this comparative example and Example 1 is that only the residue of flower and leaf Chinese medicinal herbs was used, and no raw material compatibility was carried out. All other conditions are the same as in Example 1.

[0033] The biochar and pyrolysis gas yields of Examples 1, 1, and 2 show that there is a synergistic effect between the biochemical components (cellulose, hemicellulose, lignin) and inorganic minerals (ash) of the residues from different medicinal parts, which jointly enhances the stability of the carbon structure and the carbon fixation capacity, significantly improving the biochar yield. Furthermore, an optimal balance is achieved among the biochar yield, pyrolysis oil yield, and combustible gas yield, resulting in co-production. Comparative Example 1 (pure rhizomes) has a high lignin content, but it tends excessively to undergo secondary cracking during pyrolysis, resulting in the lowest biochar yield. While the combustible gas yield may be relatively high, the H2 / CO ratio is not ideal. Comparative Example 2 (pure flowers and leaves) has the highest biochar yield due to its high ash content, but the carbon may be loose and have a poor pore structure. Simultaneously, its pyrolysis oil yield is low and of poor quality, and the combustible gas yield is also limited, with a similarly unsatisfactory H2 / CO ratio. Example 1 effectively avoids the extreme pyrolysis tendency of a single raw material by combining root and stem crops with flower and leaf crops in a ratio of 1.5:1. The synergistic catalytic effect of different medicinal parts and residues significantly increases the H2 content in combustible gas, making the H2 / CO ratio reach about 2:1, which is extremely beneficial for downstream chemical utilization.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that the pyrolysis temperature is 350°C, while the other conditions are the same as in Example 1.

[0035] Under these comparative conditions, most of the high-molecular polymers in the raw materials (such as cellulose and lignin) failed to undergo deep carbonization and decomposition, and a large amount of volatile matter was not fully released, remaining in the solid. This resulted in a seemingly high char yield, but in reality, it contained a large amount of incompletely carbonized organic matter and was not stable biochar. At the same time, due to incomplete pyrolysis, the generation of large-molecule condensable gases (oil) was relatively small, and the generation of small-molecule combustible gases (such as CO, H2, and CH4) was also limited. However, in relative proportion, because both solid and liquid products were small, the calculated combustible gas yield was high, but insufficient temperature led to incomplete conversion and low co-production efficiency.

[0036] Comparative Example 4 The difference between this comparative example and Example 1 is that the heating rate is 30°C / min, while the other conditions are the same as in Example 1.

[0037] The excessively rapid heating rate used in this comparative example caused the material to undergo a severe thermal shock in a very short time, resulting in the rapid precipitation of volatiles. This led to the violent disintegration of unreacted intermediate products and the microcrystalline structure of biochar, causing a sharp drop in the yield of solid biochar. A large amount of volatiles with moderate molecular weight were carried out of the reactor before secondary cracking, thus condensing to obtain the most pyrolysis oil. At the same time, a large amount of small molecule gas was also generated, resulting in the highest yield of combustible gas. However, this method comes at the cost of sacrificing the biochar yield, which is inconsistent with the original intention of co-production. Moreover, excessively rapid heating is not conducive to the formation of high-quality biochar with a well-developed pore structure.

[0038] Comparative Example 5 The difference between this comparative example and Example 1 is that pure nitrogen gas is introduced during the pyrolysis process, and a mixed gas is not used; the other conditions are the same as in Example 1.

[0039] This comparative example uses pure nitrogen pyrolysis, which is a purely oxygen-deficient pyrolysis. The reaction is mild, but the energy utilization efficiency and conversion depth are insufficient. Due to the lack of synergistic effect of oxidative exothermic reaction, the biochar yield and quality, as well as the combustible gas yield, are not as good as those of the example.

[0040] Comparative Example 6 The difference between this comparative example and Example 1 is that a tube furnace is used for pyrolysis instead of microwave pyrolysis; all other conditions are the same as in Example 1.

[0041] In this comparative example, a tubular furnace was used for pyrolysis. The yields of biochar and pyrolysis gas were significantly lower than in Comparative Example 1. This shows that using a microwave pyrolysis device can produce more pyrolysis oil and pyrolysis gas than using a conventional tubular furnace. This is because microwave-assisted pyrolysis utilizes the thermal effect of microwaves to heat the substances. During microwave heating, the substances absorb microwave energy and convert it into their own heat energy. The conversion from microwave energy to heat energy is very rapid, and the temperature rise of the substances is significantly faster than in traditional heat transfer heating processes. Furthermore, during microwave pyrolysis, microwaves selectively heat the medicinal residue without heating the entire space inside the pyrolysis furnace. The temperature of the medicinal residue is higher than the temperature of the surrounding space. The effect of this heating method is that the organic matter rapidly heats up and undergoes pyrolysis. After the pyrolysis products escape, they enter the surrounding space with a lower temperature, preventing secondary cracking reactions. Microwave pyrolysis rapidly decomposes organic matter, increasing the yield of pyrolysis oil and pyrolysis gas.

[0042] Table 1 Based on the data from Examples 1-3, Comparative Examples 1-6, and Table 1, this invention successfully achieved the optimal balance between biochar yield, pyrolysis oil yield, and combustible gas yield by combining different medicinal parts of medicinal residues, microwave pyrolysis, and introducing an appropriate amount of oxygen. This effectively avoids the extreme pyrolysis tendency of a single raw material, while obtaining high-quality biochar and combustible gas, achieving the goal of high efficiency and synergistic co-production.

[0043] Figure 2 (a) is the thermogravimetric analysis curve of the medicinal residue in Example 1. Figure 2 (b) and Figure 2 (c) Thermogravimetric analysis results for Comparative Example 1 and Example 2 are shown in the figure. It can be seen that at 700℃, the biochar obtained after raw material compatibility treatment exhibits higher char yield and gas yield. Raw material compatibility significantly improves the quality of the product: on the one hand, the specific surface area of ​​the biochar obtained from the pyrolysis of the mixed biochar is 113.4 m². 2 The H2 / CO ratio (2:1) of the combustible gas was significantly higher than that of a single raw material, revealing that different biochemical components (such as the dense lignin in the rhizome and the loose cellulose in the leaves and flowers) interacted during pyrolysis, jointly constructing a more developed and stable pore structure. On the other hand, the H2 / CO ratio of the combustible gas was significantly increased, indicating that the synergistic effect promoted the generation of hydrogen-rich gas, greatly improving the quality and utilization value of the combustible gas. In summary, this formulation strategy not only achieved balanced optimization of yield but also achieved synergistic enhancement in product quality.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing combustible gas and co-generated biochar from traditional Chinese medicine residue by pyrolysis / gasification, characterized in that, Specifically, the following steps are included: (1) The wet-based Chinese medicine residues of different medicinal parts are dried and then crushed and sieved to obtain Chinese medicine residue powder; (2) Microwave pyrolysis / gasification of Chinese herbal medicine residue powder to obtain biochar and gas; (3) The gas obtained in step (2) is condensed and collected to obtain non-condensable pyrolysis gas and condensed pyrolysis oil.

2. The method for producing combustible gas and co-generated biochar from the pyrolysis / gasification of traditional Chinese medicine residue according to claim 1, characterized in that, The wet-based Chinese medicine residues of different medicinal parts mentioned in step (1) include root and rhizome Chinese medicine residues and flower and leaf Chinese medicine residues, wherein the wet-based mass ratio of root and rhizome Chinese medicine residues to flower and leaf Chinese medicine residues is 1.5~4:

1.

3. The method for producing combustible gas and co-generated biochar from the pyrolysis / gasification of traditional Chinese medicine residue according to claim 1, characterized in that, The moisture content of the wet-based Chinese medicine residue mentioned in step (1) is 70%~85%.

4. The method for producing combustible gas and co-generated biochar from the pyrolysis / gasification of traditional Chinese medicine residue according to claim 1, characterized in that, The drying process described in step (1) is as follows: air dry naturally at room temperature for 24 hours, and then dry at 80~120℃ to constant weight.

5. The method for producing combustible gas and co-generated biochar from the pyrolysis / gasification of traditional Chinese medicine residue according to claim 1, characterized in that, The particle size of the Chinese herbal medicine residue powder mentioned in step (1) is 20~60 mesh.

6. The method for producing combustible gas and co-generated biochar from the pyrolysis / gasification of traditional Chinese medicine residue according to claim 1, characterized in that, The microwave pyrolysis / gasification treatment in step (2) specifically involves pyrolysis for 30 to 60 minutes at a heating rate of 5 to 25°C / min and a temperature of 400 to 900°C, while maintaining a mixed gas flow during the pyrolysis process.

7. The method for producing combustible gas and co-generated biochar from traditional Chinese medicine residue by pyrolysis / gasification according to claim 5, characterized in that, The mixed gas is composed of nitrogen and oxygen, wherein oxygen accounts for 5% to 10% of the volume of the mixed gas, and the remainder is nitrogen.

8. The method for producing combustible gas and co-generated biochar from the pyrolysis / gasification of traditional Chinese medicine residue according to claim 5, characterized in that, The flow rate of the mixed gas is 40~60 mL / min.

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