Method for preparing humic acid by improving hydrothermal reaction conversion biomass and organic fertilizer

Abstract

The invention belongs to the technical field of humic acid synthesis, and relates to a method for preparing humic acid by improving hydrothermal reaction conversion biomass and an organic fertilizer. The invention provides a method for preparing humic acid by improving hydrothermal reaction conversion biomass, which comprises the following steps: mixing a biomass raw material with water or an aqueous solution, and then carrying out hydrothermal reaction, before the hydrothermal reaction is carried out, hydrothermal pretreatment is carried out, and the hydrothermal pretreatment is carried out for 0.5-3 hours at the temperature of 100-140 DEG C under normal pressure or pressurization. Tests show that through hydrothermal pretreatment, the humic acid prepared by converting biomass through hydrothermal reaction can be effectively improved. The product prepared by the method provided by the invention or a liquid-phase product obtained by solid-liquid separation of the product has better fertility as an organic fertilizer.

Description

Technical Field

[0001] The invention belongs to the technical field of humic acid synthesis, and relates to a method for improving the preparation of humic acid by converting biomass through hydrothermal reaction, and an organic fertilizer. Background Art

[0002] Biomass resources, such as agricultural waste (straw, rice husk, etc.), forestry waste, urban organic waste, etc., have the advantages of large quantity and renewability, but their traditional treatment methods often have problems such as low efficiency and heavy pollution. Therefore, it is particularly important to find efficient and environmentally friendly ways to utilize biomass resources. Hydrothermal reaction technology has become one of the important means of biomass resource utilization because it can achieve efficient conversion of biomass under relatively mild conditions. Humic acid is an important type of organic matter that is widely present in natural environments such as soil and coal. It has multiple functions, such as being used as an organic fertilizer, soil conditioner, fertilizer enhancer, adsorbent, catalyst, etc., and has broad application prospects in agriculture, environmental protection, industry and other fields. However, traditional humic acid production mainly relies on non-renewable resources such as coal, and there are problems such as resource depletion and environmental pollution. Therefore, it is of great practical significance to develop humic acid production methods and realize the high-value utilization of biomass resources.

[0003] Hydrothermal treatment technology refers to a treatment technology in which water vaporization in a closed container at a high temperature (generally above 100°C) produces a high saturated vapor pressure, causing the treated material to undergo a physical and chemical reaction. Hydrothermal reactions are usually carried out at high temperatures, but compared with other thermochemical methods, their reaction conditions are relatively mild, easy to control, and have low equipment requirements. Hydrothermal reactions can effectively promote the decomposition and transformation of organic matter in biomass to generate humic acid products with specific structures and properties. In the process of preparing humic acid by hydrothermal reaction, the following steps are usually adopted: the biomass raw materials are pretreated by crushing, drying, etc. to improve their reaction activity; the pretreated biomass raw materials are mixed with water or aqueous solution and placed in a high-pressure reactor, heated to a certain temperature and maintained for a certain period of time for hydrothermal reaction. During the reaction, the organic matter in the biomass undergoes decomposition, polymerization and other reactions under hydrothermal conditions to generate products such as humic acid. At present, the problem of low humic acid yield is generally solved to a certain extent by optimizing hydrothermal reaction parameters such as raw materials, reaction pressure, reaction time, and additionally adding water-soluble inorganic metal hydroxides and / or catalysts to promote the conversion of biomass into humic acid. Summary of the invention

[0004] The purpose of the present invention is to further improve the yield of humic acid prepared by hydrothermal reaction conversion of biomass in a simple and low-cost manner. To this end, the present invention provides a method for improving the preparation of humic acid by hydrothermal reaction conversion of biomass and an organic fertilizer to solve this need in the art.

[0005] The present invention mixes the biomass raw material with water or an aqueous solution to perform a hydrothermal reaction. The present invention has no special requirements on the type of the biomass raw material, and any biomass raw material known in the art can be used, such as one or more of crop straw, forest processing waste, livestock and poultry manure, microalgae, and kitchen waste. In the present invention, when the biomass raw material is crop straw and / or livestock and poultry manure, the particle size of the crop straw and livestock and poultry manure is preferably below 40 meshes. In the present invention, the crop straw preferably includes corn straw, and the livestock and poultry manure preferably includes chicken manure.

[0006] Those skilled in the art may optionally adjust the process parameters of the hydrothermal reaction according to actual production needs. Generally speaking, in the hydrothermal reaction, the solid-liquid ratio of the biomass raw material to water or aqueous solution is 0.5 to 5 g:10 mL, and the reaction time is 0.5 to 5 h. In the present invention, the solid-liquid ratio of the biomass raw material to water or aqueous solution is preferably 1 g:10 mL, and the reaction time is 1 h.

[0007] On the one hand, the present invention provides a method for improving the hydrothermal reaction to convert biomass into humic acid, which comprises: mixing a biomass raw material with water or an aqueous solution, and then conducting a hydrothermal reaction to obtain a product containing humic acid; before the hydrothermal reaction, a hydrothermal pretreatment is performed, and the hydrothermal pretreatment is a treatment at 100 to 140° C. for 0.5 to 3 hours under normal pressure or pressure.

[0008] Furthermore, in the method for improving the hydrothermal reaction to convert biomass to prepare humic acid provided by the present invention, during the hydrothermal pretreatment and / or the hydrothermal reaction, a gas containing CO2 or a gas containing O2 is pressurized to 1 to 10 MPa;

[0009] The pressure or pressurized gas for the hydrothermal pretreatment and the hydrothermal reaction may be the same or different.

[0010] Furthermore, in the method for improving the hydrothermal reaction to convert biomass to prepare humic acid provided by the present invention, the concentration of CO2 in the CO2-containing gas is not less than 60%, and the concentration of O2 in the O2-containing gas is not less than 60%.

[0011] Furthermore, in the method for improving the hydrothermal reaction to convert biomass into humic acid provided by the present invention, the biomass raw material is steam exploded before the hydrothermal pretreatment.

[0012] Furthermore, in the method for improving the hydrothermal reaction to convert biomass into humic acid provided by the present invention, the steam explosion time is 0.5 to 30 minutes, and the temperature is 140 to 230°C.

[0013] Furthermore, in the method for preparing humic acid by improving the hydrothermal reaction conversion of biomass provided by the present invention, the initial pressure of the steam explosion is 0.5-8Mpa.

[0014] Furthermore, in the method for improving the hydrothermal reaction to convert biomass into humic acid provided by the present invention, a water-soluble inorganic metal hydroxide and / or a catalyst is added during the hydrothermal reaction.

[0015] Furthermore, in the method for improving the hydrothermal reaction to convert biomass to prepare humic acid provided by the present invention, the water-soluble inorganic metal hydroxide is selected from at least one of sodium hydroxide, calcium hydroxide and potassium hydroxide;

[0016] The catalyst is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate and hydrogen peroxide.

[0017] Adding a water-soluble inorganic metal hydroxide and / or a catalyst during the hydrothermal reaction is a method commonly used by those skilled in the art to improve the hydrothermal reaction to convert biomass into humic acid. In the technical solution provided by the present invention, for the convenience of implementation, a water-soluble inorganic metal hydroxide and / or a catalyst can be added in any step of steam explosion, hydrothermal pretreatment, and hydrothermal reaction. In the present invention, the water-soluble inorganic metal hydroxide and / or the catalyst are preferably added in the hydrothermal reaction step.

[0018] Furthermore, in the method for improving the hydrothermal reaction to convert biomass to prepare humic acid provided by the present invention, the mass ratio of the water-soluble inorganic metal hydroxide to the biomass raw material is 5 to 20:100;

[0019] The mass ratio of the catalyst to the biomass raw material is 0.1-0.5:100.

[0020] On the other hand, the present invention relates to an organic fertilizer, wherein the organic fertilizer comprises a product obtained by the method for improving the hydrothermal reaction to convert biomass into humic acid or a liquid product obtained after solid-liquid separation of the product.

[0021] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0022] The present invention verifies that hydrothermal pretreatment is different from extending the hydrothermal reaction time. It can better promote the humification process of organic matter, so that the generation rate of organic acid substances such as humic acid and fulvic acid is accelerated, thereby improving the final yield of humic acid. The hydrothermal pretreatment described in the present invention is essentially to carry out two hydrothermal reactions. The present invention verifies that compared with the same length of time, hydrothermal pretreatment (i.e., two hydrothermal reactions) can significantly improve the efficiency of hydrothermal reaction conversion of biomass to prepare humic acid, while increasing the hydrothermal reaction to three times or more is relatively low compared to two hydrothermal reactions, and affects production efficiency.

[0023] Steam explosion is a pretreatment technology that combines physics and chemistry. Its basic principle is to heat organic matter in a high-pressure steam environment to vaporize the water inside it. When the high pressure is released quickly, the explosion effect of the steam will cause the structure of the organic matter to break and decompose rapidly. The present invention further adopts steam explosion pretreatment, and the depolymerization effect of biomass is significant. Refractory substances such as cellulose and lignin are decomposed into smaller molecules, which are more easily degraded and humified by microorganisms, thereby increasing the yield of humic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a test flow chart of the present invention. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are available on the market unless otherwise specified. The % in the following embodiments are all mass percentages unless otherwise specified. The ratios in the following embodiments are all mass ratios unless otherwise specified.

[0027] Example 1

[0028] This example provides a method for preparing humic acid by converting biomass through conventional hydrothermal reaction as a comparison with the prior art.

[0029] Raw materials: 10 g chicken manure, 100 mL water, 2 g water-soluble inorganic metal hydroxide (KOH), and 0.01 g catalyst (H2O2).

[0030] The chicken manure is crushed to less than 40 meshes, and placed in a high-pressure reactor with water, water-soluble inorganic metal hydroxide, and a catalyst. The temperature is set to 120°C through the controller, and the operation is started after the cover is added. After reaching the set hydrothermal residence time (1h), the reactor is closed. After natural cooling, the material in the reactor is taken out and placed in a centrifuge for solid-liquid separation to obtain a liquid product. The liquid product is stirred with an appropriate amount of ammonium nitrate and an appropriate amount of potassium oxide, and then finely filtered and packaged to make liquid organic fertilizer.

[0031] Example 2

[0032] This example provides a method for preparing humic acid by converting biomass through conventional hydrothermal reaction as a comparison with the prior art.

[0033] Raw materials: corn straw 10g, water 100mL, water-soluble inorganic metal hydroxide (NaOH:CaOH=2:3) 0.2g+0.3g, catalyst (Na2CO3:NaHCO3:K2CO3:KHCO3) 0.02g+0.01g+0.01g+0.01g.

[0034] The corn stalks are crushed to less than 40 meshes, placed in a high-pressure reactor with water and water-soluble inorganic metal hydroxides, and the temperature is set to 120°C through the controller. The reactor is started after the cover is added. After the set hydrothermal residence time (1h) is reached, the reactor is closed. After natural cooling, the substances in the reactor are taken out and placed in a centrifuge for solid-liquid separation to obtain a liquid product. The liquid product is stirred with an appropriate amount of ammonium nitrate and an appropriate amount of potassium oxide, and then finely filtered and packaged to make liquid organic fertilizer.

[0035] Example 3

[0036] This example compares Example 1 with Example 2, sets different reaction conditions, and measures the humic acid content in the liquid phase product under different reaction conditions.

[0037] The test steps are as follows:

[0038] (1) Steam explosion

[0039] The biomass raw material is subjected to steam explosion, the steam explosion time is 0.5 to 30 minutes, the temperature is 140 to 230° C., and the initial pressure of the steam explosion is 0.5 to 8 MPa.

[0040] (2) Hydrothermal pretreatment

[0041] The product after steam explosion is mixed with water and placed in a high-pressure reactor, pressurized to 1-10 MPa at normal pressure or one of gas containing CO2 and gas containing O2, and treated at 100-140°C for 0.5-3h.

[0042] (3) Hydrothermal reaction

[0043] The product after hydrothermal pretreatment is subjected to hydrothermal reaction with reference to Example 1 or Example 2. During the hydrothermal reaction, the normal pressure or one of the gas containing CO2 and the gas containing O2 is pressurized by 1 to 10 MPa. The concentration of CO2 in the CO2-containing gas is not less than 60%, and the concentration of O2 in the O2-containing gas is not less than 60%. The CO2-containing gas or O2-containing gas with a purity lower than 100% is obtained by mixing CO2 or O2 with air to a desired ratio.

[0044] Different test schemes are set based on the above test steps, as shown in Table 1.

[0045] Table 1: Experimental plan

[0046]

[0047]

[0048] Referring to the test scheme provided in Table 1, the humic acid content in the liquid phase product was measured by titration. The test results are shown in Table 2.

[0049] Table 2: Test results

[0050]

[0051] As can be seen from Table 2, steam explosion, hydrothermal pretreatment, pressurization of gas containing CO2 or gas containing O2 in hydrothermal pretreatment, and pressurization of gas containing CO2 or gas containing O2 in hydrothermal reaction, the above steps can effectively improve the efficiency of hydrothermal reaction to convert biomass to prepare humic acid, and can be superimposed on each other to achieve a synergistic effect. After multiple tests, steam explosion has the greatest impact, and even increases the content of humic acid by an order of magnitude. The present invention verifies that the effects of improving the efficiency of hydrothermal reaction to convert biomass to prepare humic acid are steam explosion, pressurization of gas containing O2 in hydrothermal pretreatment and / or hydrothermal reaction, pressurization of gas containing CO2 in hydrothermal pretreatment and / or hydrothermal reaction, and hydrothermal pretreatment. In addition, after testing, using air for pressurization has a lower impact on the efficiency of hydrothermal reaction to convert biomass to prepare humic acid. Considering the additional production cost brought by the pressurizing equipment, it is not considered in actual production.

[0052] As described above, the basic principle, main features and advantages of the present invention are well described. The above embodiments and descriptions are only descriptions of the preferred implementation modes of the present invention, and the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, various changes and improvements made by ordinary technicians in this field to the technical solution of the present invention should fall within the protection scope determined by the present invention.

Claims

1. A method for improving the hydrothermal reaction to convert biomass into humic acid, comprising: The biomass raw material is mixed with water or an aqueous solution, and then a hydrothermal reaction is carried out to obtain a product containing humic acid, characterized in that a hydrothermal pretreatment is carried out before the hydrothermal reaction, and the hydrothermal pretreatment is carried out at 100 to 140° C. for 0.5 to 3 hours under normal pressure or pressure.

2. The method according to claim 1, characterized in that During the hydrothermal pretreatment and / or the hydrothermal reaction, the gas containing CO2 or the gas containing O2 is pressurized to 1-10 MPa; The pressure or pressurized gas for the hydrothermal pretreatment and the hydrothermal reaction may be the same or different.

3. The method according to claim 1, characterized in that The concentration of CO2 in the CO2-containing gas is not less than 60%, and the concentration of O2 in the O2-containing gas is not less than 60%.

4. The method according to any one of claims 1 to 3, characterized in that: Before the hydrothermal pretreatment, the biomass raw material is subjected to steam explosion.

5. The method according to claim 4, characterized in that The steam explosion time is 0.5 to 30 minutes, and the temperature is 140 to 230°C.

6. The method according to claim 4, characterized in that The initial pressure of the steam explosion is 0.5-8Mpa.

7. The method according to claim 1, characterized in that A water-soluble inorganic metal hydroxide and / or a catalyst is added during the hydrothermal reaction.

8. The method according to claim 7, characterized in that The water-soluble inorganic metal hydroxide is selected from at least one of sodium hydroxide, calcium hydroxide and potassium hydroxide; The catalyst is at least one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate and hydrogen peroxide.

9. The method according to claim 7, characterized in that: The mass ratio of the water-soluble inorganic metal hydroxide to the biomass raw material is 5 to 20:100; The mass ratio of the catalyst to the biomass raw material is 0.1-0.5:

100.

10. An organic fertilizer, characterized in that: The organic fertilizer comprises a product obtained by the method according to any one of claims 1 to 9 or a liquid product obtained after solid-liquid separation of the product.

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