Method for preparing composite porous carbon material from biomass waste residue and phosphogypsum and application thereof

Abstract

This invention belongs to the field of solid waste resource utilization technology, and discloses a method for preparing composite porous carbon materials using biomass waste residue and phosphogypsum, and its application. The biomass waste residue is washed, dried, crushed, and carbonized to obtain biochar. The biochar is then uniformly mixed with phosphogypsum to obtain a biochar-phosphogypsum composite porous carbon material. The composite porous carbon material is then subjected to a gasification reaction under a carbon dioxide atmosphere to generate high-calorific-value combustible carbon monoxide and high-value-added calcium sulfide. This invention features a simple process and achieves the synergistic high-value utilization of two typical solid wastes: biomass waste residue and phosphogypsum. It not only provides an effective way to utilize organic solid waste and phosphogypsum, but also efficiently converts them into clean energy and high-value by-products, resulting in significant environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a method for preparing composite porous carbon materials using biomass waste residue and phosphogypsum, and its application. Background Technology

[0002] The continuous expansion of industries such as agriculture, food processing, traditional Chinese medicine manufacturing, and livestock and poultry farming has generated a large amount of biomass solid waste while ensuring supply. This biomass solid waste has a high water content, is easily perishable, and has a complex composition. Currently, it is still commonly disposed of through landfill, open-air dumping, or simple incineration. This not only occupies a large amount of land resources, but the leachate, odors, and greenhouse gases such as methane produced during the decomposition process also pose a continuous threat to the surrounding environment. Although there are resource utilization technologies such as composting, feed production, or direct combustion for power generation, they generally face problems such as low added value of products, high energy consumption, difficulty in controlling secondary pollution, or limited application scope. As a result, a large amount of biomass waste residue has not been utilized at high value and efficiency, becoming a constraint on the green transformation of related industries.

[0003] On the other hand, the problem of phosphogypsum solid waste stockpiling, a byproduct of the phosphate chemical industry, is particularly prominent. Phosphogypsum contains impurities such as residual acid, soluble phosphorus, fluorine, and trace heavy metals. Long-term open-air stockpiling can easily cause groundwater and soil pollution, posing a significant environmental risk. Existing resource utilization pathways for phosphogypsum mainly focus on the building materials sector, such as the preparation of gypsum board and cement retarders. However, these pathways have limitations such as limited disposal capacity, low added value of products, and high requirements for raw material purity, making it difficult to achieve large-scale and efficient resource utilization.

[0004] Currently, research and practice on the resource utilization of biomass waste and phosphogypsum, two major types of solid waste, are largely independent and lack systematic coordination. Traditional technological approaches are mostly limited to the treatment of single-type wastes, failing to fully utilize the complementary potential of the two materials in terms of their physicochemical properties—for example, biochar is rich in carbon sources and has well-developed pores, while phosphogypsum can act as a catalyst or auxiliary agent for gasification reactions under certain conditions. Developing a technology that can co-process both types of solid waste and transform them into high-value-added energy or material products can not only alleviate environmental pressure simultaneously but also help improve resource recycling efficiency and promote the circular economy to a deeper level.

[0005] Therefore, there is an urgent need to develop a simple technology that can effectively integrate two types of solid waste and achieve their high-value transformation. This invention is proposed against this backdrop, aiming to provide an innovative approach for the large-scale disposal and resource utilization of these two major types of solid waste through the synergistic transformation of biomass waste residue and phosphogypsum. Summary of the Invention

[0006] This invention provides a method for preparing composite porous carbon materials using biomass waste residue and phosphogypsum, and its high-value application, aiming to achieve the synergistic resource utilization of the two types of solid waste and promote the in-depth development of the circular economy.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing composite porous carbon materials from biomass waste residue and phosphogypsum, comprising the following steps: S1. The washed, dried and crushed biomass waste residue is placed in a closed tube furnace for thermal decomposition reaction, cooled and sieved to obtain biochar powder. S2. Dry the phosphogypsum and sieve it to obtain pretreated phosphogypsum; S3. Biochar powder and pretreated phosphogypsum are ground and mixed to obtain biochar-phosphogypsum composite porous carbon material.

[0008] In step S1, the biomass waste includes at least one of the following: Chinese medicine residue, straw, bagasse, coffee grounds, sawdust, and livestock and poultry manure.

[0009] In step S1, the washing conditions include: mixing biomass waste residue and deionized water in a water bath stirring pot for 60-120 minutes, with a water bath temperature of 20-60°C and a stirring rate of 100-300 r / min, followed by filtration and rinsing with deionized water 3-5 times.

[0010] In step S1, the drying temperature is 80~110℃ and the time is 12~24h.

[0011] In step S1, the pulverizing speed is 200~400 r / min and the time is 1~5 min.

[0012] In step S1, the conditions for thermal decomposition include: placing the pulverized biomass in a closed tube furnace, heating and carbonizing it under a N2 atmosphere, with an N2 flow rate of 20-50 mL / min and a heating rate of 10-30 °C / min, heating to 500-700 °C and holding for 1-3 hours, cooling to room temperature, pulverizing and passing through an 80-100 mesh sieve to obtain biochar.

[0013] In step S2, the phosphogypsum is a large-scale industrial solid waste generated during the wet process of producing phosphoric acid in a phosphate chemical enterprise.

[0014] In step S2, the drying process involves placing the phosphogypsum at 80-110°C for 12-24 hours.

[0015] In step S3, the biochar powder and pretreated phosphogypsum are mixed at a mass ratio of 15:1 to 1:15, ground for 1 to 20 minutes, and after being mixed evenly, a biochar-phosphogypsum composite porous carbon material is obtained.

[0016] In a second aspect, the present invention provides a biochar-phosphogypsum composite porous carbon material prepared by the method, which is used for CO2 gasification reduction to produce CO, and produces calcium sulfide (CaS) solid product as a byproduct.

[0017] The specific method for applying the biochar-phosphogypsum composite porous carbon material to CO2 gasification reduction to prepare CO and produce CaS solid by-product is as follows: The biochar-phosphogypsum composite porous carbon material is placed in a tube furnace and heated under a N2 protective atmosphere at a flow rate of 50-100 mL / min and a heating rate of 5-30 °C / min. When the temperature reaches 800-1000 °C, it is kept at this temperature and CO2 is introduced to carry out the gasification reaction at a flow rate of 100-200 mL / min. CO is then prepared, and a calcium-sulfur-rich by-product mainly composed of CaS is obtained.

[0018] The present invention has the following beneficial effects: The biochar-phosphogypsum composite porous carbon material obtained by this invention is applied in CO2 gasification reduction reaction. Through the synergistic reaction of the biochar-phosphogypsum composite porous carbon material under CO2 atmosphere, not only can CO2 resources be converted into high-calorific-value combustible gas with CO as the main component, but the thermal decomposition temperature of phosphogypsum can also be significantly reduced, so that it can be stably converted into solid by-products with CaS as the main component, thereby realizing the efficient recovery and value-added utilization of calcium and sulfur resources.

[0019] The process of this invention is simple and easy to implement, with widely available raw materials and low cost, making it easy to achieve large-scale production. It can simultaneously treat two types of bulk solid waste, significantly reducing the cost and environmental risks of their separate disposal, promoting the transformation of waste into resources, meeting the requirements of circular economy and high-quality development, and the technical path has both significant carbon emission reduction benefits and economic feasibility. It helps to achieve the reduction, stabilization and high value of solid waste, and has positive significance for promoting the green and low-carbon transformation of related industries and achieving carbon neutrality goals. Attached Figure Description

[0020] Figure 1 Here is a SEM image of the four-angled grass charcoal from Example 1; Figure 2 This is a SEM image of the porous carbon material made from *Symplocos buergeriana* charcoal and phosphogypsum in Example 1. Figure 3 The image shows the XRD pattern of the solid product after CO2 gasification of the *Symplocos buergeriana* charcoal-phosphogypsum composite porous carbon material in Example 1. Figure 4 The results of the CO2 conversion efficiency and CO selectivity test of the *Symplocos buergeriana* charcoal-phosphogypsum composite porous carbon material in Application Example 1 are shown. Figure 5The results of the CO2 conversion efficiency and CO selectivity test of the Magnolia officinalis carbon-phosphogypsum composite porous carbon material in Example 2 are shown. Figure 6 The results of CO2 conversion efficiency and CO selectivity tests of the eucalyptus wood chip charcoal-phosphogypsum composite porous carbon material in Example 3 are used. Figure 7 The XRD pattern of the solid product of phosphogypsum powder after CO2 gasification in Application Example 4; Figure 8 The results of the CO2 conversion efficiency and CO selectivity test of the four-angled grass charcoal in Comparative Example 1 are shown. Figure 9 This is a schematic diagram of the preparation method and application process of the composite porous carbon material made from biomass waste residue and phosphogypsum according to the present invention. Detailed Implementation

[0021] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. Various improvements and changes can be made to the specific embodiments described in this specification without departing from the scope or spirit of the present invention, which will be obvious to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. The specification and embodiments are merely exemplary.

[0022] Unless otherwise stated, the technical and scientific terms used in this invention have the same meanings as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention. In the event of any conflict with any other document, the contents of this specification shall prevail.

[0023] Example 1 A method for preparing a porous carbon material composed of *Symplocos buergeriana* charcoal and phosphogypsum. In this embodiment, the *Symplocos buergeriana* waste residue was provided by a pharmaceutical factory in Yunnan Province, and the phosphogypsum was generated during the wet process of phosphoric acid production in a phosphate chemical plant in Yunnan Province. The specific preparation steps are as follows: (1) The waste residue of *Symplocos buergeriana* was mixed with deionized water in a water bath stirring pot. The waste residue was submerged in deionized water and stirred for 120 min. The water bath temperature was 30℃ and the stirring rate was 200 r / min. After filtration, it was rinsed with deionized water 3 times. Then, it was dried in an oven at 105℃ for 12 h. Then, it was crushed in a pulverizer at a speed of 300 r / min for 2 min to obtain *Symplocos buergeriana* residue. The *Symplocos buergeriana* residue was placed in a closed tube furnace and heated and carbonized in a N2 atmosphere. The N2 flow rate was 50 mL / min and the heating rate was 20℃ / min. It was heated to 600℃ and kept at that temperature for 2 h. After cooling to room temperature, it was crushed and passed through a 100-mesh sieve to obtain *Symplocos buergeriana* biochar powder. (2) Dry the phosphogypsum in an oven at 100°C for 12 hours and then sieve it to obtain pretreated phosphogypsum; (3) The prepared *Symplocos buergeriana* biochar powder and pretreated phosphogypsum were mixed at a mass ratio of 8:1, ground for 5 minutes, and mixed evenly to obtain *Symplocos buergeriana* char-phosphogypsum composite porous carbon material.

[0024] Figure 1 , Figure 2 The images show scanning electron microscope (SEM) images of single *Symplocos buergeriana* biochar and *Symplocos buergeriana*-phosphogypsum composite porous carbon materials. As can be seen from the images, the *Symplocos buergeriana* biochar has a regular structure and a smooth and flat surface. After mixing with phosphogypsum, phosphogypsum components are attached to the surface and pores of the carbon.

[0025] Example 2 A method for preparing a composite porous carbon material of Magnolia officinalis carbon and phosphogypsum. In this embodiment, the Magnolia officinalis waste residue was provided by a pharmaceutical factory in Yunnan Province, and the phosphogypsum was generated during the wet process of phosphoric acid production in a phosphate chemical plant in Yunnan Province. The specific preparation steps are as follows: (1) The waste residue of Magnolia officinalis and deionized water were placed in a water bath stirring pot, and the waste residue was submerged in deionized water and mixed and stirred for 100 min. The water bath temperature was 20℃ and the stirring rate was 300 r / min. After filtration, the residue was rinsed with deionized water 4 times. Then, it was dried in an oven at 80℃ for 24 h and then crushed in a pulverizer at a speed of 400 r / min for 1 min to obtain Magnolia officinalis residue. The Magnolia officinalis residue was placed in a closed tube furnace and heated and carbonized in a N2 atmosphere. The N2 flow rate was 20 mL / min and the heating rate was 10℃ / min. The temperature was heated to 500℃ and held for 3 h. After cooling to room temperature, it was crushed and passed through a 90 mesh sieve to obtain Magnolia officinalis biomass char powder. (2) Dry the phosphogypsum in an oven at 80°C for 24 hours and then sieve it to obtain pretreated phosphogypsum; (3) The prepared Magnolia officinalis biochar powder and pretreated phosphogypsum were mixed at a mass ratio of 9:1, ground for 10 minutes, and mixed evenly to obtain Magnolia officinalis char-phosphogypsum composite porous carbon material.

[0026] Example 3 A method for preparing a eucalyptus wood chip charcoal-phosphogypsum composite porous carbon material is disclosed. In this embodiment, the eucalyptus wood chip is provided by a timber mill in Yunnan Province, and the phosphogypsum is derived from the wet phosphoric acid production process of a phosphoric acid chemical company in Yunnan Province. The specific preparation steps are as follows: (1) Eucalyptus wood chips and deionized water were mixed in a water bath stirring pot, with the waste residue submerged in deionized water and stirred for 60 min. The water bath temperature was 60℃ and the stirring rate was 100 r / min. After filtration, the mixture was rinsed 5 times with deionized water. Then, it was dried in an oven at 110℃ for 14 h and then crushed in a pulverizer at a speed of 200 r / min for 5 min to obtain eucalyptus wood chip residue. The eucalyptus wood chip residue was placed in a closed tube furnace and heated and carbonized under N2 atmosphere. The N2 flow rate was 30 mL / min and the heating rate was 30℃ / min. The mixture was heated to 700℃ and held for 1 h. After cooling to room temperature, it was crushed and passed through an 80 mesh sieve to obtain eucalyptus wood chip biochar powder. (2) Dry the phosphogypsum in an oven at 110°C for 15 hours and then sieve it to obtain pretreated phosphogypsum; (3) The eucalyptus wood chip biochar powder and pretreated phosphogypsum were mixed at a mass ratio of 10:1, ground for 20 minutes, and mixed evenly to obtain eucalyptus wood chip biochar-phosphogypsum composite porous carbon material.

[0027] Example 4 (1) The phosphogypsum produced in the wet process of phosphoric acid production in a certain phosphoric acid chemical plant in Yunnan was dried in an oven at 100℃ for 12 hours to obtain pretreated phosphogypsum; (2) Grind the pretreated phosphogypsum for 5 minutes and mix it evenly to obtain phosphogypsum powder.

[0028] Application Example 1 Take 2g of the porous carbon material of *Symplocos buergeriana* charcoal-phosphogypsum composite obtained in Example 1, place it in a tube furnace, and heat it under a N2 protective atmosphere at a heating rate of 15℃ / min. When the temperature reaches 900℃, keep it at that temperature and introduce CO2 to carry out a gasification reaction. The CO2 concentration is 20%, and the total gas flow rate is 150mL / min.

[0029] Application Example 2 Take 2g of the magnolia charcoal-phosphogypsum composite porous carbon material obtained in Example 2, place it in a tube furnace, and heat it under a N2 protective atmosphere at a heating rate of 5℃ / min. When the temperature reaches 1000℃, keep it at that temperature and introduce CO2 to carry out a gasification reaction. The CO2 concentration is 20% and the total gas flow rate is 100mL / min.

[0030] Application Example 3 Take 2g of the eucalyptus wood chip char-phosphogypsum composite porous carbon material obtained in Example 3, place it in a tube furnace, and heat it under a N2 protective atmosphere at a heating rate of 30℃ / min. When the temperature reaches 800℃, keep it at that temperature and introduce CO2 to carry out a gasification reaction. The CO2 concentration is 20% and the total gas flow rate is 200mL / min.

[0031] Application Example 4 Take 2g of the phosphogypsum powder obtained in Example 4, place it in a tube furnace, and heat it under a N2 protective atmosphere at a heating rate of 15℃ / min. When the temperature reaches 900℃, keep it at that temperature and introduce CO2 to carry out a gasification reaction. The CO2 concentration is 20% and the total gas flow rate is 150mL / min.

[0032] Comparative Example 1 Take 2g of the *Symplocos buergeriana* biochar powder from Example 1, place it in a tube furnace, and heat it under a N2 protective atmosphere at a rate of 15℃ / min. When the temperature reaches 900℃, keep it at that temperature and introduce CO2 for gasification reaction. The CO2 concentration is 20%, and the total gas flow rate is 150mL / min.

[0033] Comparative Example 2 Take 2g of Magnolia officinalis biochar powder from Example 2, place it in a tube furnace, and heat it under a N2 protective atmosphere at a heating rate of 5℃ / min. When the temperature reaches 1000℃, keep it at that temperature and introduce CO2 to carry out a gasification reaction. The CO2 concentration is 20% and the total gas flow rate is 100mL / min.

[0034] Comparative Example 3 Take 2g of eucalyptus wood chip biochar powder from Example 3, place it in a tube furnace, and heat it under a N2 protective atmosphere at a rate of 30℃ / min. When the temperature reaches 800℃, keep it at that temperature and introduce CO2 for gasification reaction. The CO2 concentration is 20% and the total gas flow rate is 200mL / min.

[0035] The test results of CO2 gasification reaction in the application examples and comparative examples are shown in Table 1.

[0036] Table 1

[0037] Note: " / " indicates that no CaS was generated or not detected.

[0038] The experimental results in Table 1 show that the CO2 conversion rate of single biochar is significantly lower than that of the biochar-phosphogypsum composite porous carbon material. The composite porous materials prepared in Examples 1 to 3 all exhibit higher conversion rates. Under the same reaction conditions, single phosphogypsum powder cannot generate CO, and the highest SO2 concentration detected during the test was 0.58%, with CaSO4 as the main product. Figure 7 As shown in the figure, no CaS was detected, indicating that under the same experimental conditions, the thermal decomposition of phosphogypsum did not generate high-value CaS, and sulfur was mainly converted into gaseous SO2. Furthermore, the thermal decomposition efficiency of phosphogypsum was significantly lower than that of the composite material. This further verifies that the synergistic thermal decomposition of biochar and phosphogypsum in this invention helps reduce the reaction conditions required for the thermal decomposition of phosphogypsum alone, and allows both types of waste residue to generate more valuable byproducts.

[0039] Taking the experimental results of the *Symplocos buergeriana* charcoal-phosphogypsum composite porous carbon material as an example, the main solid products after the reaction are CaS and SiO2, of which CaS accounts for about 87% (e.g., ...). Figure 3 As shown), the CO2 conversion rate can be maintained above 95% within 90 minutes, and the CO gain rate is close to 100% (e.g.). Figure 4 As shown); meanwhile, the composite porous carbon material made from magnolia bark and eucalyptus wood chips mixed with phosphogypsum showed good CO2 conversion rates at different reaction times (e.g. Figure 5 , 6 As shown); under the same reaction conditions, single phosphogypsum powder cannot produce CO, and the maximum SO2 concentration detected during the test was 0.58%, with CaSO4 being the main product (as shown). Figure 7 As shown), CaS products were not detected. The CO2 conversion rate of the *Symplocos buergeriana* biochar obtained in Comparative Example 1 was significantly lower than that of the *Symplocos buergeriana* biochar-phosphogypsum composite porous carbon material in Application Example 1 (e.g., ...). Figure 8 (As shown).

[0040] The above experimental results show that, regardless of whether it is *Symplocos buergeriana*, *Magnolia officinalis*, eucalyptus wood chips, or other organic waste materials referred to in this invention, the biochar-phosphogypsum composite porous carbon material prepared by combining with phosphogypsum according to the method of this invention exhibits better reaction performance than single biochar under CO2 gasification reaction conditions. At the same time, it can stably obtain a higher proportion of high-value CaS byproducts than the thermal decomposition of single phosphogypsum.

[0041] like Figure 9 The diagram shows the preparation method and application process of the composite porous carbon material made from biomass waste residue and phosphogypsum according to the present invention. It can be seen that the present invention uses biomass waste residue and waste phosphogypsum as raw materials to prepare porous carbon materials and applies them in the CO2 gasification reduction reaction. Through the synergistic reaction of biomass carbon-phosphogypsum composite porous materials under CO2 atmosphere, not only can CO2 resources be converted into high-calorific-value combustible gas with CO as the main component, but the thermal decomposition temperature of phosphogypsum can also be significantly reduced, converting it into solid products with CaS as the main component, thereby realizing the efficient recovery and value-added utilization of calcium and sulfur resources.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a composite porous carbon material from biomass waste residue and phosphogypsum, characterized in that, Includes the following steps: S1. The washed, dried and pulverized biomass waste residue is subjected to thermal decomposition reaction, cooled and sieved to obtain biochar powder. S2. Dry the phosphogypsum and sieve it to obtain pretreated phosphogypsum; S3. Biochar powder and pretreated phosphogypsum are ground and mixed to obtain biochar-phosphogypsum composite porous carbon material.

2. The method for preparing composite porous carbon materials from biomass waste residue and phosphogypsum according to claim 1, characterized in that, In step S1, the biomass waste residue is at least one of the following: Chinese medicine residue, straw, bagasse, coffee grounds, sawdust, and livestock and poultry manure.

3. The method according to claim 1, wherein the biomass waste residue and phosphogypsum are mixed at a ratio of 1:1 to 1:

3. In step S1, the washing involves mixing biomass waste residue with deionized water and stirring in a water bath for 60-120 minutes at a water bath temperature of 20-60°C and a stirring rate of 100-300 r / min, followed by filtration and rinsing with deionized water 3-5 times. ​ 4. The method for preparing composite porous carbon materials from biomass waste and phosphogypsum according to claim 1, characterized in that, In step S1, the drying temperature is 80~110℃ and the time is 12~24h; the pulverizing speed is 200~400r / min and the time is 1~5min.

5. The method for preparing composite porous carbon materials from biomass waste and phosphogypsum according to claim 1, characterized in that, In step S1, the thermal decomposition is carried out under a N2 atmosphere with a N2 flow rate of 20-50 mL / min, heating to 500-700°C at a heating rate of 10-30°C / min and holding for 1-3 hours, then cooling to room temperature, pulverizing and passing through an 80-100 mesh sieve.

6. The method for preparing composite porous carbon materials from biomass waste and phosphogypsum according to claim 1, characterized in that, In step S2, the phosphogypsum is an industrial solid waste generated during the wet process of producing phosphoric acid in a phosphate chemical enterprise.

7. The method for preparing composite porous carbon materials from biomass waste and phosphogypsum according to claim 1, characterized in that, In step S2, the drying process involves placing the phosphogypsum at 80-110°C for 12-24 hours.

8. The method for preparing composite porous carbon materials from biomass waste and phosphogypsum according to claim 1, characterized in that, In step S3, the mass ratio of biochar powder to pretreated phosphogypsum is 15:1 to 1:15, and the mixture is ground for 1 to 20 minutes.

9. The application of the composite porous carbon material prepared by the method of claim 1 in the CO2 gasification reduction to prepare CO and calcium sulfide.

10. The application according to claim 9, specifically the method is as follows: the biochar-phosphogypsum composite porous carbon material is heated under a N2 protective atmosphere, the N2 flow rate is 50~100mL / min, the heating rate is 5~30℃ / min, and when the temperature reaches 800~1000℃, CO2 is introduced to carry out a gasification reaction, the CO2 flow rate is 100~200mL / min, CO is prepared, and calcium sulfide product is also obtained.

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