阅读说明：本技术 富钾缓释生物炭及其制备方法与应用 (Potassium-rich slow-release biochar and preparation method and application thereof ) 是由 陈冠益 武文竹 颜蓓蓓 钟磊 孙于茹 崔孝强 李健 于 2020-05-29 设计创作，主要内容包括：一种富钾缓释生物炭及其制备方法与应用。该制备方法包括将沼渣和生物质直燃底灰按照质量比9∶1至4∶1混合,将所得混合原料经密闭热解制得所述富钾缓释生物炭。本发明制备方法简单,提升了生物炭钾的缓释效果,拓宽了沼气工程及生物质发电工程的副产物利用思路,提升了生物质资源化利用效率。(A potassium-rich slow-release biochar and a preparation method and application thereof. The preparation method comprises the steps of mixing biogas residues and biomass direct-fired bottom ash according to the mass ratio of 9: 1 to 4: 1, and carrying out closed pyrolysis on the obtained mixed raw materials to obtain the potassium-rich slow-release biochar. The preparation method is simple, the slow release effect of the biochar potassium is improved, the by-product utilization ideas of biogas engineering and biomass power generation engineering are widened, and the biomass resource utilization efficiency is improved.)

1. A preparation method of potassium-rich slow-release biochar is characterized by comprising the following steps:

mixing the biogas residues and the biomass direct-fired bottom ash according to the mass ratio of 9: 1 to 4: 1, and carrying out closed pyrolysis on the obtained mixed raw materials to obtain the potassium-rich slow-release biochar.

2. The method according to claim 1, wherein the total potassium content of the biogas residue is not less than 8000 mg/kg.

3. The method according to claim 1, wherein the biogas residue has a particle size of 10 to 60 mesh.

4. The method according to any one of claims 1 to 3, wherein the biogas residue is prepared by:

and naturally drying the fresh biogas residues, drying at constant temperature, crushing and sieving to obtain the biogas residues.

5. The preparation method of claim 1, wherein the total potassium content of the biomass direct-fired bottom ash is not less than 26000 mg/kg.

6. The preparation method according to claim 1, wherein the particle size of the biomass direct-fired bottom ash is larger than 60 meshes.

7. The preparation method according to claim 1, 5 or 6, wherein the biomass direct-fired bottom ash is prepared by the following steps:

using crop waste as a direct-fired raw material, and obtaining bottom ash through combustion; removing incomplete combustion residues and gravels in the bottom ash to obtain the biomass direct-fired bottom ash.

8. The preparation method according to claim 1, wherein the closed pyrolysis conditions of the mixed raw materials are as follows: heating to 500 plus or minus 25 ℃ in a muffle furnace at a heating rate of 10 plus or minus 1 ℃/min, and then preserving heat for 2 h.

9. The potassium-rich slow-release biochar prepared by the preparation method of the potassium-rich slow-release biochar according to any one of claims 1 to 8.

10. Use of the potassium-rich slow-release biochar of claim 9 in a fertilizer.

Technical Field

The invention relates to the technical field of biomass resource utilization, in particular to potassium-rich slow-release biochar and a preparation method and application thereof.

Background

Potassium is one of three major elements for crop growth, and is a recognized 'quality element'. The potassium fertilizer consumed in China each year accounts for about 30% of the world, but the potassium utilization efficiency of crops is only 10% -20%. The unused potash fertilizer is easy to cause soil pollution, crop yield reduction and serious resource waste. Based on the integral target requirement of 'two-reduction one-control three-basic' of Ministry of agriculture, the environment-friendly slow-release fertilizer becomes a research hotspot. The slow release fertilizer can release nutrients for a long time and has a certain improvement effect on soil. However, the current slow release fertilizers for agricultural applications usually achieve the purpose of controlling the release of nutrients by means of coating granulation or mixing of inhibitors/dissolution inhibitors and the like. The traditional process is complex, and a partial film coating material is not easy to degrade, so that the development of the slow release fertilizer industry is limited. Research shows that the biochar serving as an environment-friendly renewable porous material can hold nutrient ions and reduce the leaching rate of inorganic fertilizer, so that the biochar is widely applied to agricultural environments.

The biochar contains rich nutrient elements, and the nutrient content of the soil can be improved by applying the biochar to the soil. The raw material selection, nutrient element form and structural characteristics all influence the fertilizer application characteristics. The biogas residues are used as byproducts of biogas engineering, and contain 30-50% of organic matters, 10-20% of humic acid, 0.8-2% of total nitrogen, 0.4-1.2% of total phosphorus and 0.6-2% of total potassium. The biogas residues are high-quality carbon-making raw materials, and return to the field after carbonization can avoid agricultural risks and fully utilize nutrients. At present, a high-efficiency organic fertilizer carbon fertilizer is disclosed, which is prepared by taking crop straws, biogas residues, biogas slurry, excrement and the like as raw materials, can be directly returned to fields for utilization, does not need additional fertilizer, but has a complex process and no sustained and controlled release effect.

Currently, biochar is commonly used as a fertilizer carrier or used as one of raw materials of a coated slow-release fertilizer core, or is applied together with other fertilizers, but few researches focus on the potential of biochar as a fertilizer and a nutrient controlled-release technology of biochar in the preparation process. Therefore, how to provide the biochar with high nutrient content, particularly high potassium content, and a slow release effect is an urgent problem to be solved.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a potassium-rich slow-release biochar, and a preparation method and an application thereof, so as to at least partially solve at least one of the above-mentioned technical problems.

In order to achieve the purpose, the invention adopts the following specific scheme:

as one aspect of the invention, the invention provides a preparation method of potassium-rich slow-release biochar, which comprises the following steps: mixing the biogas residues and the biomass direct-fired bottom ash according to the mass ratio of 9: 1 to 4: 1, and carrying out closed pyrolysis on the obtained mixed raw materials to obtain the potassium-rich slow-release biochar.

As another aspect of the invention, the potassium-rich slow-release biochar prepared by the preparation method of the potassium-rich slow-release biochar is provided.

As a further aspect of the invention, the application of the potassium-rich slow-release biochar in the fertilizer is provided.

Based on the technical scheme, the invention has the advantages that:

the raw material for preparing the charcoal has autocatalysis potential, the yield of the biochar is increased, the yield of the fixed carbon is increased, and the quality of fertilizer products is greatly improved.

The total potassium content of the biochar prepared by the method is improved compared with that of biochar with a single biomass component, and meanwhile, the total nutrient content of nitrogen, phosphorus and potassium of the biochar meets the national standard of organic fertilizers.

The slow-release biochar prepared by the invention can slowly release K in water⁺The release rate is obviously reduced in the first 5 days, and K is reduced in 28 days⁺The cumulative release rate slows down.

The preparation method is simple, the raw materials are wide in source, the high-value performance of the effective components in the raw materials is fully considered, the problem of disposal of the biomass energy utilization technology by-products is solved, and the method has good economic and ecological benefits.

Drawings

FIG. 1 is a flow chart of the preparation of potassium-rich slow-release biochar according to examples 1-2 of the present invention;

FIG. 2 is a graph showing the total potassium content in the potassium-rich biochar and feedstock of examples 1-2 and comparative example 1;

FIG. 3 is a graph showing yields of potassium-rich biochar and fixed carbon in examples 1-2 and comparative example 1;

FIG. 4 shows K of potassium-rich biochar in examples 1-2 and comparative example 1⁺Cumulative release tendency。

Detailed Description

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

In order to meet the demand of urgent need for reasonable utilization of biogas residues and biomass direct-fired bottom ash, the invention prepares potassium-rich slow-release biochar by pyrolyzing and carbonizing a mixture of the biogas residues and the biomass direct-fired bottom ash based on the consideration that metal in ash can catalyze a biomass pyrolysis process and change the structural nutrient characteristics of the biochar, and the biomass direct-fired bottom ash is used as a catalyst and a quick-acting potassium source to catalyze the pyrolysis of the biogas residues and can regulate and control the conversion of water-soluble potassium to an exchange state and a non-exchange state, so that the potassium-rich slow-release biochar is obtained, the problems of insufficient potassium content, low quick-acting potassium content and convertible potassium content of the traditional biochar can be solved, and the potassium-rich slow-release biochar has the great advantages of high potassium.

Specifically, the invention provides a preparation method of potassium-rich slow-release biochar, which comprises the following steps: mixing the biogas residues and the biomass direct-fired bottom ash according to the mass ratio of 9: 1 to 4: 1, and carrying out closed pyrolysis on the obtained mixed raw materials to obtain the potassium-rich slow-release biochar.

It is worth mentioning that the biomass direct-fired bottom ash is a traditional quick-acting farmyard potash fertilizer, the mass content of the ash is generally over 98%, and the biomass direct-fired bottom ash is an effective pyrolysis catalyst. The content of potassium is as high as about 23.2g/kg, and 90 percent of potassium element in the potassium is water-soluble, so the long-acting use is difficult. However, by catalyzing the biogas residue for pyrolysis, the yield and the gas quality of the biochar are increased, and the conversion of water-soluble potassium to an exchange state and a non-exchange state can be regulated and controlled simultaneously, so that the biochar rich in potassium for slow release is obtained.

Wherein, the total potassium content of the biogas residues is not lower than 8000mg/kg, and if the total potassium content is too low, the potassium content in the prepared potassium-rich slow-release biochar can be influenced; the grain diameter of the biogas residues is 10 meshes to 60 meshes, so that the biogas residues can be uniformly mixed with the direct-fired bottom ash in the follow-up process.

Wherein the biogas residue is prepared by the following steps: and naturally drying the fresh biogas residues, drying at constant temperature, crushing and sieving to obtain the biogas residues.

Wherein the total potassium content of the biomass direct-fired bottom ash is not lower than 26000mg/kg, and if the total potassium content is too low, the potassium content in the prepared potassium-rich slow-release biochar can be influenced; the particle size of the biological direct-fired bottom ash is larger than 60 meshes so as to remove sand and incompletely-fired biomass existing in the direct-fired bottom ash.

Wherein, the biogas residue and the biomass direct-fired bottom ash are mixed according to the mass ratio of 9: 1 to 4: 1, for example, 9: 1, 8: 1, 7: 1, 6: 1, 5: 1 and 4: 1, if the content of the biomass direct-fired bottom ash is too low, the yield of the fixed carbon is not improved, the slow release capability is not strong, and if the content of the biomass direct-fired bottom ash is too high, the content of the fixed carbon in the product is reduced.

The biomass direct-fired bottom ash is prepared by the following steps: using crop waste as a direct-fired raw material, and obtaining bottom ash through combustion; removing incomplete combustion residues and gravels in the bottom ash to obtain the biomass direct-fired bottom ash. The crop waste comprises one or more of straw, rice straw and the like.

Wherein, the closed pyrolysis conditions of the mixed raw materials are as follows: heating to 500 plus or minus 25 ℃ in a muffle furnace at a heating rate of 10 plus or minus 1 ℃/min, and then preserving heat for 2 h.

The invention also provides the potassium-rich slow-release biochar prepared by the preparation method, which can reach the nutrient standard of organic fertilizers, is novel potassium-rich biochar with the slow-release fertilizer characteristic, is simple, convenient and easy to obtain, is expected to improve the utilization rate of the potassium fertilizer of the biochar, and realizes the resource utilization of wastes and the sustainable development of agriculture.

The invention also provides application of the prepared potassium-rich slow-release biochar in a fertilizer. The potassium-rich slow-release biochar is applied to soil in a simulation mode, and has the potential of improving the concentration and the content of the long-acting potassium of the soil; meanwhile, the invention has simple process and low production cost, can greatly reduce the application amount and the application frequency of the fertilizer, and reduce the environmental pollution and ecological damage caused by unreasonable treatment of agricultural wastes and unreasonable application of the fertilizer.

The technical solution of the present invention will be described in detail below by referring to a plurality of specific examples. It should be noted that the following specific examples are only for illustration and are not intended to limit the invention. In the embodiment of the invention, the total potassium content of the biogas residues is about 8458 mg/kg; the total potassium content of the biomass ash is about 26933 mg/kg.