Method for preparing humic acid by activating coal gasification slag, soil improvement material and application thereof

Abstract

The present application provides a method for preparing humic acid by activating coal gasification slag, a soil improvement material and its application, and relates to the technical field of resource utilization of coal gasification slag, comprising the following steps: mixing coal gasification slag with organic activation matrix to form a biological reactor; the organic activation matrix comprises at least one of livestock and poultry manure and its compost; the biological reactor is reacted under aerobic conditions, so that the stable carbon structure in the coal gasification slag is biologically activated, and the generation of humic acid and the conversion of fulvic acid to humic acid are promoted, and a soil improvement material is obtained. The present application not only has simple process and low energy consumption, is conducive to the high-value resource utilization of coal gasification slag, but also can significantly improve the content of humic acid and the stability of total humic acid, the product has no obvious ecological toxicity, and is conducive to the improvement of barren soil and the improvement of farmland soil nutrients.

Description

Technical Field

[0001] This invention relates to the technical field of resource utilization of coal gasification slag, and in particular to a method for activating coal gasification slag to prepare humic acid, soil amendment materials, and their applications. Background Technology

[0002] Coal gasification slag is one of the main solid wastes generated during the coal gasification process, and its harmless treatment and resource utilization have become prominent issues facing the coal gasification industry. Coal gasification slag is rich in carbonaceous materials and various mineral components, but its organic matter structure is stable and its activity is low, making it difficult for microorganisms to directly utilize, thus limiting its direct application in agriculture and the ecological environment.

[0003] Regarding the application of coal gasification slag in soil improvement, existing technologies have attempted to enhance its utilization value through physical or chemical means. Existing technology CN108464221A discloses a method for preparing expandable granules from coal gasification slag through secondary high-temperature treatment, and then incorporating municipal sludge and microbial agents to prepare a saline-alkali soil improvement matrix. This method improves the utilization rate of mineral components in coal gasification slag to some extent, but the introduction of municipal sludge poses a risk of heavy metal pollution, and the amount that can be added is limited, making long-term and large-scale application difficult. Existing technology CN117363364A discloses a method for preparing saline-alkali soil conditioner through multi-step fermentation of coal gasification slag with specific microbial strains and kitchen waste, improving the safe utilization of coal gasification slag. However, the process is complex, requires a variety of chemical reagents in large quantities, and has specific requirements for microbial strains, limiting the widespread adoption of the technology.

[0004] In addition, existing technologies attempt to use coal gasification slag as an auxiliary material for organic fertilizer or artificial soil. Existing technology CN105777427A discloses a method for preparing organic fertilizer mixed with coal gasification slag, obtaining organic fertilizer from coal gasification slag by adding straw, sugars, fermentation agents, and chemical fertilizers. Existing technologies CN120441402A and CN119908287A use coal gasification slag as a low-proportion adsorbent or composting conditioner for the co-treatment of livestock and poultry manure and the preparation of artificial soil. However, the above technologies generally use livestock and poultry manure or other organic waste as the main raw materials, with a low amount of coal gasification slag used. This fails to fully utilize its potential as an organic carbon source and does not effectively improve its carbon structure stability, high aromaticity, and poor microbial availability. Consequently, the formation efficiency of humic acid, especially humic acid, in the composting system is low, the conversion process from fulvic acid to humic acid lacks effective control, and the overall increase in humic acid content is limited.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for activating coal gasification slag to prepare humic acid, which can solve the problem that coal gasification slag is difficult to effectively humify in traditional composting systems due to its stable organic carbon structure, high degree of aromatization, and poor microbial availability.

[0007] The second objective of this invention is to provide a soil amendment material with high humic acid content, good stability of total humic acid, no obvious ecotoxicity, and beneficial for improving barren soil and enhancing soil nutrients in farmland.

[0008] The third objective of this invention is to provide an application of a soil amendment material that can achieve outstanding application results.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, a method for preparing humic acid by activating coal gasification slag includes the following steps: Coal gasification slag is mixed with an organic activated matrix to form a bioreactor; The organic activated matrix includes at least one of livestock and poultry manure and its composted products; The bioreactor is subjected to aerobic conditions to activate the stable carbon structure in the coal gasification slag, while promoting the generation of humic acid and the conversion of fulvic acid to humic acid, thus obtaining soil amendment materials.

[0010] Furthermore, the particle size of the coal gasification slag is no greater than 2 mm.

[0011] Furthermore, the organic carbon content of the gasification slag is 20 wt% to 45 wt%.

[0012] Furthermore, the livestock and poultry manure includes at least one of chicken manure, pig manure, cow manure, and sheep manure.

[0013] Furthermore, the weight ratio of the coal gasification slag to livestock and poultry manure is 1:4 to 3:2.

[0014] Furthermore, the composted product is obtained by aerobic composting of livestock and poultry manure with wheat husks, cotton stalks and / or fungal residue; Preferably, the weight ratio of the livestock and poultry manure to wheat husks, cotton stalks and / or mushroom residue is 3:1 to 6:1; Preferably, the weight ratio of the coal gasification slag to the decomposed product is 1:1 to 4:1.

[0015] Furthermore, the bioreactor has a water content of 45% to 55%. Preferably, the reaction temperature of the bioreactor is 30 ℃~60 ℃, more preferably 45 ℃~55 ℃; Preferably, the reaction time of the bioreactor is 30 to 50 days.

[0016] Furthermore, the humic acid content is increased by 6% to 25%; Preferably, the humic acid content is increased by 11% to 122%.

[0017] Secondly, a soil amendment material is prepared by the method described in any of the above-mentioned methods.

[0018] Thirdly, the application of the aforementioned soil amendment material in the improvement of barren soil and the enhancement of soil nutrients in farmland.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a method for preparing humic acid by activating coal gasification slag. Using coal gasification slag as a mineral structure carrier and potential carbon skeleton donor, and livestock and poultry manure or its composted products as an organic activation matrix, an aerobic biological reaction system is constructed to carry out the humification reaction. This method can activate the stable carbon structure in the coal gasification slag. The surface of the aromatic carbon and silica-alumina minerals rich in the coal gasification slag serves as a reaction interface for microbial metabolites, inducing the conversion of fulvic acid to humic acid, effectively improving the stability of the humic acid structure. In summary, the present invention is not only simple in process and low in energy consumption, which is conducive to the high-value resource utilization of coal gasification slag, but also significantly improves the humic acid content and the stability of total humic acid. The product has no obvious ecotoxicity and is beneficial for improving barren soil and enhancing soil nutrients in farmland.

[0020] The soil amendment material provided by this invention has a high humic acid content, good stability of total humic acid, and no obvious ecotoxicity, which is beneficial to the improvement of barren soil and the enhancement of soil nutrients in farmland.

[0021] The application of the soil amendment material provided by this invention can achieve outstanding results. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0023] According to a first aspect of the present invention, a method for preparing humic acid by activating coal gasification slag is provided, comprising the following steps: Coal gasification slag is mixed with an organic activated matrix to form a bioreactor; Organic activated substrates include at least one of livestock and poultry manure and its composted products; The bioreactor is used to conduct reactions under aerobic conditions, which bioactivates the stable carbon structure in the coal gasification slag, while promoting the generation of humic acid and the conversion of fulvic acid to humic acid, thus obtaining soil amendment materials.

[0024] The method of this invention achieves the activation of coal gasification slag and the increase of humic acid content by bio-composting coal gasification slag with livestock and poultry manure or its composted products. It is not only simple, convenient, low-cost, low-carbon and efficient, which is conducive to the high-value resource utilization of coal gasification slag, but also significantly improves the humic acid content and the stability of total humic acid. The product has no obvious ecotoxicity and is beneficial to the improvement of barren soil and the enhancement of soil nutrients in farmland.

[0025] In a preferred embodiment, the particle size of the coal gasification slag is no greater than 2 mm, which is more conducive to the full reaction of the bioreactor.

[0026] In this invention, the coal gasification slag can be naturally air-dried to remove particles larger than 2 mm, and the organic carbon content of the coal gasification slag can be 20 wt% to 45 wt%.

[0027] In a preferred embodiment, livestock and poultry manure includes, but is not limited to, at least one of chicken manure, pig manure, cow manure, and sheep manure.

[0028] In this invention, the weight ratio of coal gasification slag to livestock and poultry manure can be 1:4 to 3:2, which is more conducive to the full reaction of the bioreactor.

[0029] In a preferred embodiment, the composted product can be obtained by aerobic composting of livestock and poultry manure with wheat husks, cotton stalks and / or mushroom residue. The initial carbon-to-nitrogen ratio of the compost can be 25-30, and the weight ratio of livestock and poultry manure to wheat husks, cotton stalks and / or mushroom residue can be 3:1 to 6:1.

[0030] In this invention, the weight ratio of coal gasification slag to composted product can be 1:1 to 4:1, which is more conducive to the full reaction of the bioreactor.

[0031] In a preferred embodiment, the water content of the bioreactor can be 45% to 55%.

[0032] In a preferred embodiment, the reaction temperature of the bioreactor can be 30°C to 60°C, with typical but non-limiting reaction temperatures such as 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, and 60°C, and more preferably 45°C to 55°C; natural ventilation is ensured, and the reaction time of the bioreactor can be 30 days to 50 days, with typical but non-limiting reaction times such as 30 days, 40 days, and 50 days.

[0033] The reaction system of this invention, under suitable microbial humification reaction temperature and moisture content conditions, is more conducive to promoting the bioactivation of stable carbon structures in coal gasification slag and promoting the conversion of fulvic acid to humic acid, thus more effectively improving the stability of humic acid and maximizing the resource utilization of coal gasification slag.

[0034] In this invention, the humic acid content after reaction can reach 18 g / kg to 51 g / kg, which is 11% to 122% higher than the initial value, and the total humic acid content can reach 24 g / kg to 76 g / kg, which is 6% to 25% higher than the initial value.

[0035] According to a second aspect of the present invention, a soil amendment material is provided, which is prepared by the method described in any of the preceding claims.

[0036] The soil amendment material of this invention has a high humic acid content, good stability of total humic acid, and no obvious ecotoxicity, which is beneficial to the improvement of barren soil and the enhancement of soil nutrients in farmland.

[0037] According to a third aspect of the present invention, the above-described soil amendment material is provided for the improvement of barren soil and the enhancement of soil nutrients in farmland, and can achieve outstanding application results.

[0038] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0039] Examples 1-3 Examples 1-3 provide a method for preparing humic acid by activating coal gasification slag, comprising the following steps: The coal gasification slag is mixed with livestock and poultry manure, and the moisture content of the mixture is adjusted to 50% to form a bioreactor. The livestock and poultry manure is cow dung (moisture content 25%). In Examples 1-3, the weight ratios of coal gasification slag to cow dung were 1:4, 2:3, and 3:2, respectively. Coal gasification slag provides a mineral carrier and stable structure for composting and humification reactions. Coal gasification slag is a solid byproduct formed after the ungasified residual carbon and minerals melt and cool after the organic carbon of coal is partially converted into syngas, which is mainly composed of CO and H2, at high temperatures. The organic carbon content of coal gasification slag is 20 wt%~45 wt%, and its mineral components include aluminosilicate minerals and alkaline and iron oxides. The coal gasification slag is obtained by air drying and removing particles larger than 2 mm. The bioreactor is subjected to humification under aerobic conditions at a temperature of 50 °C. This process activates the stable carbon structure in the coal gasification slag, promotes the generation of humic acid and the conversion of fulvic acid to humic acid. When the temperature of the reactor exceeds 50 °C, the reactor is turned over to ensure sufficient oxygen supply. The reaction cycle is 40 days, resulting in soil amendment material.

[0040] Table 1 shows the test results before and after the reaction in Examples 1-3. It can be seen that the total humic acid (humic acid and fulvic acid) content increased by 0.3 g / kg to 3 g / kg, with an increase rate of 8% to 15%. The humic acid content increased by 6 g / kg to 13 g / kg, with an increase rate of 42% to 122%. These results indicate that the biomass reaction of coal gasification slag and livestock manure can activate the organic carbon in the coal gasification slag to form humic acid, especially humic acid. Furthermore, after 40 days of reaction, the seed germination index (GI) was 105% to 131%, indicating no ecotoxicity and that it can be used as a soil fertility improver.

[0041] The determination of total humic acid content, humic acid content, and fulvic acid content should refer to the commonly used methods for determining humic substances in the agricultural industry. The specific steps are as follows: (1) Weigh 5 g of the sample to be tested, place it in a 250 mL Erlenmeyer flask, add 100 mL of a mixture of 0.1 mol / L NaOH and 0.1 mol / L Na4P2O7, keep it at 25 °C and shake for 24 h, centrifuge (4000 r / min, 10 min) and take the supernatant. (2) Take 50 mL of supernatant, adjust the pH to 1.0~1.5 with 6 mol / L hydrochloric acid, let stand overnight to precipitate humic acid, centrifuge to separate the precipitate (humic acid), and the supernatant is fulvic acid solution; (3) Wash the humic acid precipitate with water 2-3 times and transfer it to a weighing bottle. Dry it at 105 °C until constant weight and weigh it to calculate the humic acid content. After the fulvic acid solution is brought to volume, take a portion and determine the organic carbon by potassium dichromate volumetric method, and then convert it to fulvic acid content. The total humic acid content is the sum of the humic acid and fulvic acid contents.

[0042] Table 1

[0043] Example 4 The only difference between this embodiment and Embodiment 1 is that cow dung is replaced with chicken dung; Everything else is the same as in Example 1.

[0044] The test results before and after the reaction in this embodiment are shown in Table 2.

[0045] Table 2

[0046] Example 5 The only difference between this embodiment and Embodiment 1 is that cow dung is replaced with pig dung; Everything else is the same as in Example 1.

[0047] The test results before and after the reaction in this embodiment are shown in Table 3.

[0048] Table 3

[0049] Example 6 The only difference between this embodiment and Embodiment 1 is that cow dung is replaced with sheep dung; Everything else is the same as in Example 1.

[0050] The test results before and after the reaction in this embodiment are shown in Table 4.

[0051] Table 4

[0052] Examples 7-9 Examples 7-9 provide a method for preparing humic acid by activating coal gasification slag, comprising the following steps: The coal gasification slag is mixed with the composted livestock and poultry manure, and the moisture content of the mixture is adjusted to 50% to form a bioreactor. The composted livestock and poultry manure is obtained by mixing cow dung with crop straw and composting it. It is brownish-red in color, has no obvious odor, a carbon-to-nitrogen ratio of ≤20, and a germination index (GI) greater than 80%. In Examples 7-9, the weight ratios of coal gasification slag to composted livestock and poultry manure were 4:1, 2.5:1, and 1:1, respectively. Coal gasification slag provides a mineral carrier and stable structure for composting and humification reactions. Coal gasification slag is a solid byproduct formed after the ungasified residual carbon and minerals melt and cool after the organic carbon of coal is partially converted into syngas, which is mainly composed of CO and H2, at high temperatures. The organic carbon content of coal gasification slag is 20 wt%~45 wt%, and its mineral components include aluminosilicate minerals and alkaline and iron oxides. The coal gasification slag is obtained by air drying and removing particles larger than 2 mm. The bioreactor is subjected to humification under aerobic conditions at a temperature of 30 °C. This process activates the stable carbon structure in the coal gasification slag, promotes the generation of humic acid and the conversion of fulvic acid to humic acid, and ensures sufficient oxygen supply. The reaction cycle is 35 days, resulting in soil amendment material.

[0053] Table 5 shows the test results before and after the reaction in Examples 7-9. It can be seen that the total humic acid (humic acid and fulvic acid) content increased by 2 g / kg to 10 g / kg, with an increase rate of 6% to 25%. The humic acid content increased by 3 g / kg to 8 g / kg, with an increase rate of 11% to 20%. The above results indicate that the bio-composting reaction between coal gasification slag and composted livestock and poultry manure can activate the organic carbon in the coal gasification slag to form humic acid, especially humic acid. In addition, the seed germination index (GI) value was 78% to 127% after 35 days of reaction, indicating that there is no ecotoxicity and it can be used as a soil fertility improver.

[0054] Table 5

[0055] Examples 10-11 The only difference between Examples 10-11 and Example 9 is that the reaction temperature of the bioreactor in Examples 10-11 is 50 °C, and the weight ratio of coal gasification slag to composted livestock and poultry manure in Examples 10-11 is 4:1 and 2.5:1, respectively. Everything else is the same as in Example 9.

[0056] The test results before and after the reaction in Examples 10-11 are shown in Table 6. It can be seen that when the coal gasification slag and the composted livestock and poultry manure are mixed at a weight ratio of 2.5:1 at a reaction temperature of 50 ℃, the mixture has a better promoting effect on the formation of humic acid.

[0057] Table 6

[0058] Example 12 The only difference between this embodiment and embodiment 11 is that the reaction temperature of the bioreactor in this embodiment is 60 °C. Everything else is the same as in Example 11.

[0059] The test results before and after the reaction in Example 12 are shown in Table 7.

[0060] Table 7

[0061] Comparative Example 1 The only difference between this comparative example and Example 1 is that the coal gasification slag is replaced with straw. Everything else is the same as in Example 1.

[0062] Compared with Example 1, the drawback of this comparative example is that the straw needs to be degraded before humification, resulting in low aromaticity and poor stability of humic acid.

[0063] Comparative Example 2 The only difference between this comparative example and Example 1 is that the coal gasification slag is replaced with biochar. Everything else is the same as in Example 1.

[0064] Compared to Example 1, the drawback of this comparative example is that the cost of biochar is relatively high.

[0065] Comparative Example 3 The only difference between this comparative example and Example 7 is that the coal gasification slag is replaced with zeolite. Everything else is the same as in Example 7.

[0066] Compared to Example 7, the drawback of this comparative example is that the zeolite does not provide an organic carbon skeleton and cannot directly promote the condensation of humic acid.

[0067] In summary, the method of this invention uses coal gasification slag as a mineral structure carrier and potential carbon skeleton donor, and livestock and poultry manure or its composted products as an organic activation matrix to construct an aerobic biological reaction system for humification reaction. This can activate the stable carbon structure in coal gasification slag. The surface of the aromatic carbon and silica-alumina minerals rich in coal gasification slag serves as a reaction interface for microbial metabolites, which can induce the conversion of fulvic acid to humic acid, effectively improving the stability of the humic acid structure.

[0068] This invention not only features a simple process and low energy consumption, which is conducive to the high-value resource utilization of coal gasification slag, but also significantly improves the humic acid content and the stability of total humic acid. The product has no obvious ecotoxicity and is beneficial to the improvement of barren soil and the enhancement of soil nutrients in farmland.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing humic acid by activating coal gasification slag, characterized in that, Includes the following steps: Coal gasification slag is mixed with an organic activated matrix to form a bioreactor; The organic activated matrix includes at least one of livestock and poultry manure and its composted products; The bioreactor is subjected to aerobic conditions to activate the stable carbon structure in the coal gasification slag, while promoting the generation of humic acid and the conversion of fulvic acid to humic acid, thus obtaining soil amendment materials.

2. The method according to claim 1, characterized in that, The particle size of the coal gasification slag is no greater than 2 mm.

3. The method according to claim 1, characterized in that, The organic carbon content of the coal gasification slag is 20 wt% to 45 wt%.

4. The method according to any one of claims 1-3, characterized in that, The livestock and poultry manure includes at least one of chicken manure, pig manure, cow manure, and sheep manure.

5. The method according to claim 4, characterized in that, The weight ratio of the coal gasification slag to the livestock and poultry manure is 1:4 to 3:

2.

6. The method according to any one of claims 1-3, characterized in that, The composted product is obtained by aerobic composting of livestock and poultry manure with wheat husks, cotton stalks and / or mushroom residue. Preferably, the weight ratio of the livestock and poultry manure to wheat husks, cotton stalks and / or mushroom residue is 3:1 to 6:1; Preferably, the weight ratio of the coal gasification slag to the decomposed product is 1:1 to 4:

1.

7. The method according to any one of claims 1-3, characterized in that, The bioreactor has a water content of 45% to 55%. Preferably, the reaction temperature of the bioreactor is 30 ℃~60 ℃, more preferably 45 ℃~55 ℃; Preferably, the reaction time of the bioreactor is 30 to 50 days.

8. The method according to claim 7, characterized in that, The humic acid content is increased by 6% to 25%; Preferably, the humic acid content is increased by 11% to 122%.

9. A soil amendment material, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The application of the soil amendment material according to claim 9 in the improvement of barren soil and the enhancement of soil nutrients in farmland.

Images