CN114213167A

CN114213167A - Method for promoting aerobic compost decomposing process and improving compost quality

Info

Publication number: CN114213167A
Application number: CN202111458207.XA
Authority: CN
Inventors: 刘科; 王欣; 王悦; 李俊国; 吴昌宁; 杜春祥
Original assignee: Southwest University of Science and Technology
Current assignee: Southwest University of Science and Technology
Priority date: 2021-12-02
Filing date: 2021-12-02
Publication date: 2022-03-22

Abstract

The invention discloses a method for promoting the decomposition process of aerobic compost and improving the compost quality, which comprises the step of carrying out aerobic compost fermentation decomposition on a mixture of organic materials and decomposition-promoting mineral particles, wherein the decomposition-promoting mineral particles comprise mineral particles separated from coal or coal gangue before combustion or chemical conversion, and the chemical conversion comprises coal pyrolysis, coal gasification, coal liquefaction, coal dry distillation or coal coking. The method of the invention can promote the aerobic composting process and improve the composting quality.

Description

Method for promoting aerobic compost decomposing process and improving compost quality

Technical Field

The invention belongs to the field of organic waste resource utilization, and particularly belongs to the technical field of fermented compost.

Background

Along with the rapid development of agriculture in China, the pollution problem of agricultural wastes is increasingly highlighted. The agricultural wastes mainly comprise crop straws, agricultural product processing wastes and livestock and poultry manure. According to statistics, livestock and poultry manure is about 40 hundred million tons per year, crop straws are about 9.4 hundred million tons, and agricultural product processing waste is about 5.8 hundred million tons in China. The direct return of the straws to the field causes soil diseases and toxic action on crop seedlings, thus causing crop yield reduction; the straw combustion can increase the environmental pollution and is one of the causes of haze. The livestock excrement, a large amount of hydrogen sulfide, alcohols, phenols and aminobenzene generated by decomposition of the livestock excrement, pathogenic bacteria, pathogenic microorganisms, pathogenic egg, antibiotic resistance genes and the like in the livestock excrement seriously pollute soil and water environment and cause disease transmission.

As an effective method for recycling organic waste and hazardous waste, aerobic composting (i.e., fermentation and decomposition of organic materials by using aerobic microorganisms) has many advantages such as low production cost, less pollution, and soil improvement. However, the traditional composting process still has some defects, such as nitrogen loss, emission of greenhouse gases or foul gases, low decomposition degree and the like, and causes certain problems of environmental pollution and poor quality of organic fertilizer products.

The addition of mineral additives is one of the effective methods to overcome the above disadvantages. At present, the types of mineral additives reported are single minerals, including kaolinite, goethite, delta-MnO₂Calcium superphosphate, bayerite, zeolite, bentonite, diatomite, medical stone, lime, biochar and the like, or single mineral is compounded. The diatomite, the calcium superphosphate and the bentonite are commonly used, and other materials such as the biochar are limited in practical application due to the problems of high material cost, single action effect and the like. In addition, the mineral additive added in the prior art also has the problem of long decomposing time. Therefore, the temperature of the molten metal is controlled,the search for efficient, relatively inexpensive compost maturity promoting materials is an important issue for improving the quality of compost.

In addition, the organic fertilizer NY-T525-2021, which is the agricultural industry standard of the people's republic of China, definitely prohibits the use of the fly ash as the raw material of the organic fertilizer. The reason is that the content of heavy metals in the fly ash is often over-standard, which not only pollutes soil, but also has toxic action on fermentation microorganisms in the process of fermentation composting. Under the standard, many coal-based wastes from coal mines and coal preparation plants are not substantially exported for use as organic fertilizer raw materials.

Disclosure of Invention

The present invention is directed to solving the above problems.

The invention provides a method for promoting the decomposition process of aerobic compost and improving the compost quality, which comprises the step of carrying out aerobic compost fermentation decomposition on a mixture of organic materials and decomposition-promoting mineral particles, wherein the decomposition-promoting mineral particles comprise mineral particles separated from coal or coal gangue before combustion or chemical conversion, and the chemical conversion comprises coal pyrolysis, coal gasification, coal liquefaction, coal dry distillation or coal coking.

Wherein the organic material is selected from agriculture and forestry organic materials (including but not limited to straw, wood chips, rice hulls, rice bran, wheat bran, corncobs and the like), food processing organic materials (including but not limited to bean pulp, bean dregs, mushroom dregs, algae and the like), animal wastes (including but not limited to chicken manure, cow manure, sheep manure and the like), algae, kitchen wastes or any mixture thereof.

Wherein the mineral particles separated from the coal or coal gangue before combustion or chemical conversion are obtained by the following two ways:

the first method comprises the following steps: mineral particles were obtained by conventional coal flotation: the flotation is that according to the difference of the surface properties of minerals, a carbon-containing material source and the non-combustible mineral are separated through a surfactant and mechanical adjustment, and the obtained non-combustible mineral is ground to obtain micro-nano mineral particles;

in the second method, the mineral particles are obtained by a micro-mineral separation technology: the method comprises the following steps:

A. wet-milling coal or coal gangue containing non-combustible mineral substances and carbon-hydrogen-containing combustible substances in water until the average particle size of particles is less than 500 microns, and adding an additive into the water-coal-slurry in the continuous wet-milling process to fully mix and disperse the particles uniformly to obtain the micro-nano water-coal-slurry containing the additive;

B. and introducing micro-bubbles with the diameter less than 200 micrometers into the micro-nano coal water slurry containing the additive, wherein the combustible particles containing carbon and hydrogen float upwards along with the bubbles to form a floating material flow, and the mineral particles adhered with the additive agglomerate and sink as underflow to obtain the mineral particles.

Preferably, the additive is a hydrophilic nanoparticle, a collector or a surfactant, wherein the hydrophilic nanoparticle is an aluminosilicate nanoparticle, the collector is a non-polar hydrocarbon oil, and the surfactant is a surface active molecule having a hydrophilic group and a hydrophobic group.

Preferably, the aluminosilicate nanoparticles are prepared by further grinding the mineral particles separated in step B to a nanoscale range; the collecting agent is kerosene, diesel oil or artificially synthesized nonpolar hydrocarbon oil; the surfactant is pinitol oil, camphor oil, phenolic acid mixed fatty alcohol, isomeric hexanol, octanol, ether alcohol or ester substances.

The mineral particles separated from the coal or coal gangue before combustion or chemical conversion have a particle size of less than 100 μm (particle size distribution about d)₅₀<10μm,d₉₀<45 μm) and comprises kaolinite, illite, chlorite, quartz, pyrite, calcium carbonate and feldspar. Various types of minerals are distributed in a free or embedded state, for example, part of minerals such as pyrite are horizontally embedded on the surface of kaolinite in a micro-nano mode. The composite mineral has abundant effective mineral nutrients, large specific surface area and high activity (adsorption or reaction) sites due to abundant mineral composition, ultrafine particles and special mineral embedding structure.

The minerals in coal are generally composed of clay minerals (kaolinite, illite, chlorite, etc.), quartz, calcite, pyrite, etc. As shown in fig. 1, the fly ash obtained by high-temperature combustion contains a vitreous body as a main component, but the content of the crystalline substance may be relatively high, ranging from 11 to 48%. The main crystal phase substances are mullite, quartz, hematite, magnetite, tricalcium aluminate, melilite, amesite, periclase and the like, and the mullite accounts for the maximum proportion in all the crystal phase substances and can reach 6-15% of the total amount (the literature source is mineral composition of Wu-legend, Wang Zhi. fly ash (in the case of money sensation), and the fly ash is comprehensively utilized 2001,01: 26-31). In contrast, the mineral composition of the ultrafine composite minerals according to the present invention, which are not burned at high temperature, maintains the type of minerals in coal, and mainly consists of kaolinite, illite, quartz, chlorite, pyrite, calcite (fig. 2 and 3). Analytically, the cation exchange capacity of the superfine composite mineral in the research is 20-30cmol/kg, while the fly ash after combustion is only 1.2cmol/kg., which shows that the mineral is sintered or melted by high-temperature combustion, and the surface property, particularly the ion exchange capacity, is remarkably reduced.

Furthermore, the mineral particles separated from the coal or coal refuse before combustion or chemical conversion comprise one or more of the following medium trace elements essential for plant growth: B. ca, Cl, Cu, Fe, Mg, Mn, Mo, S, Se and Zn.

The mineral particles separated from the coal or coal refuse used in the present invention before combustion or chemical conversion are not limited in source, and can be obtained, for example, by the process described in another patent application (application No. 201710502714.6) entitled "a process for producing high calorific value coal-water slurry from coal or coal refuse and coal gasification process using the same" of the present applicant. The entire disclosure of this patent is incorporated herein. For the sake of brevity, detailed fabrication processes are not described again. Of course, the mineral particles in the present application can also be separated by other known or potential separation processes, and are not limited to the above-mentioned processes, as long as the mineral particles derived from coal or coal gangue are not sintered at high temperature, i.e. above 500 ℃. For the description of the "micro-mineral separation technology", reference may be made to an issued patent application by the present applicant at 2017, 9, 20, with the application numbers: 201710853445.8 entitled "a method for increasing the energy density of a liquid or gaseous fuel".

Preferably, the water content of the mixture of the organic materials and the decomposition-promoting and ripening mineral particles is adjusted to 50-70%, and the decomposition-promoting and ripening mineral particles account for 2-20% of the mass of the mixture.

Preferably, the fermentation and decomposition comprises static aerobic compost fermentation in a strip pile manner, aerobic compost fermentation in a groove manner or aerobic compost fermentation in a reactor, and the fermentation process is lightproof and heat-insulated, wherein the temperature in the high-temperature period of the fermentation is kept above 45 ℃. The compost has a heating period, a high temperature period, a cooling period and a low temperature period.

Preferably, the fermentation is done by using a naturally occurring microbial species in the organic material, or by additionally adding a microbial species to the mixture, including but not limited to photosynthetic bacteria, lactic acid bacteria, yeast bacteria, gram-positive actinomycetes or filamentous bacteria, in fact, any microorganism that can perform the fermentation function can be used.

Preferably, the organic material is organic material that has been subjected to different degrees of fermentation maturity. This means that products at different fermentation stages of conventional fermentation composts can be used as the feedstock of the present invention, and that products that have undergone fermentation decomposition by the process of the present invention can be subjected to the process of the present invention again.

Preferably, the product of the invention may also be subjected to a secondary fermentation, which may be carried out without addition of said pro-staling mineral particles.

The invention has the beneficial effects that:

1. the invention can use the mineral particles separated from the coal or coal gangue before combustion or chemical conversion as the raw material of the aerobic fermentation type organic fertilizer, because the heavy metal content of the product is lower than the national standard, the invention breaks through the limit of the industrial standard of the organic fertilizer, and finds a new application way for a large amount of waste residues of coal mining enterprises and coal preparation plants.

2. The weight ratio of the trace elements does not need to be compounded manually

The conventional method for supplementing trace elements in the current fertilizer industry is to pulverize specific ores (such as calcium magnesium ore, wollastonite, iron ore, etc.) containing specific trace elements and add the pulverized specific ores as trace element sources to fermented compost fertilizers, and in short, what is lacking and what is supplemented, and the method is not comprehensive. If various trace elements need to be systematically supplemented, ores of various trace elements need to be compounded according to a specific proportion after being crushed, and time, labor and materials are wasted.

Some fertilizer enterprises add a large amount of fly ash which is a byproduct of thermal power plants or mineral residues which are subjected to high-temperature treatment in coal chemical industry into fertilizers as trace element sources or directly use the fly ash or the mineral residues as soil conditioners, but the problem is that the mineral residues are fully sintered or vitrified after passing through a high-temperature environment in a gasification furnace, and useful mineral trace elements in the mineral residues are difficult to release under natural conditions, so that the mineral residues are difficult to absorb by plant roots, and the effect of the mineral residues as the fertilizers or the soil conditioners is very limited.

In contrast, the invention separates the mineral particles contained in the coal or coal gangue before high-temperature sintering, and the mineral particles are used as a trace element source of compost fertilizer. The mineral impurities present in raw coal are largely divided into two types, the first of which is soil or rock fragments mixed from the surrounding formation environment during the coal-making process of raw wood, which are mixed with the carbon-hydrogen containing combustibles in raw coal on a macroscopic scale and have a weak binding force. The other is mineral trace nutrient elements absorbed by the original wood from original soil by the plant root system in the growth process of the original wood, and because the mineral trace nutrient elements are symbiotic with the wood, the part of mineral impurities and the combustible containing carbon and hydrogen are mixed in a micro scale and are combined very tightly, and the binding force is strong. The conventional coal washing process and coal dressing process can only carry out primary separation on the first mineral impurities in the raw coal, but cannot effectively separate the carbon-hydrogen-containing combustible materials which are embedded with each other in the raw coal in a microscopic scale from the second mineral impurities, especially for the low-quality coal. However, the second mineral impurities are also separable by a special separation process. The mineral impurity particles in the invention are separated from hydrocarbon combustible materials before the coal or coal gangue is combusted or subjected to chemical conversion (taking coal gasification industry as an example, before coal dust or coal water slurry is gasified at high temperature before entering a gasification furnace), and the mineral impurity particles are not subjected to any high-temperature sintering treatment, so that the mineral contained in the coal or coal gangue particles is easily released under natural conditions and is absorbed by plant roots. It is easy to find the source of these mineral impurities, wherein the second mineral impurity is just the mineral nutrient absorbed by the ancient trees from the ancient soil, exists in the ancient wood, and changes into the current mineral impurity through the complex geological coal effect. Therefore, the mineral impurities are essentially mineral fertilizers which are effectively absorbed by ancient trees and stored till now, and the proportions of various trace elements are equivalently compounded by the ancient plants according to the natural absorption degree of the ancient plants, so that people do not need to compound the trace elements in proportion. Such valuable ancient fertilizers were sintered at high temperatures in current combustion or chemical conversion reactors (e.g., gasifiers) and became unabsorbed by current plants without much loss. According to the invention, all mineral particles are separated from the hydrocarbon combustible substance before combustion and chemical conversion, so that the mineral impurity particles are prevented from being sintered at high temperature, the existing form of ancient ecology is retained, and the mineral impurity particles are used as the plant mineral trace element compound fertilizer or used as a carrier for further loading other plant nutrient elements and then used as the fertilizer, and the novel creative way for realizing the maximum utilization of coal resources by changing waste into valuable is provided.

3. The decay-promoting and mature mineral particles disclosed by the invention are different from fly ash or coal gangue in properties. Compared with the fly ash: the main components in the decay-promoting and mature mineral particles are mineral particles separated from coal or coal gangue before combustion or chemical conversion, and the mineral particles are not combusted or subjected to heat treatment, wherein the crystal forms of clay minerals such as kaolinite, illite, chlorite and the like contained in the mineral particles are not changed, and partial minerals such as calcium carbonate, pyrite and the like are not subjected to thermal decomposition, so that the mineral particles have higher cation exchange capacity, richer plant available mineral nutrients (such as K, Ca, S, Fe, B and the like) and better biocompatibility. Compared with coal gangue, the coal gangue is burned or chemically converted before the coal or coal gangue is burned or chemically convertedThe mineral particles separated from the mineral oil have finer particle size (particle size less than 100 μm, particle size distribution about d)₅₀<10μm,d₉₀<45 μm)), lower quartz-based mineral content, higher available mineral nutrients and cation exchange capacity (about 30 cmol/kg); the larger specific surface area can provide more carrier space and active sites for microorganisms, promote the fermentation process and catalyze the formation and accumulation of humus (the catalysis of clay minerals is indirectly realized mainly by accelerating the formation of phenolic substances).

4. The corrosion-promoting and ripening mineral particles used in the invention are rich in various oxides (aluminum oxide, iron oxide, manganese oxide, silicon oxide and the like) and surface functional groups, can catalyze the decomposition and humification processes of organic materials, and promote the yield of total humins polymers. In addition, the addition of the composite mineral can properly shorten the high-temperature period of the composting process and reduce the nitrogen loss and the emission of malodorous gases. On the other hand, metabolites (such as acetic acid, oxalic acid, butyric acid and the like) in the composting process can further activate mineral elements (K, Ca, B, Si, Se and the like) in the superfine composite minerals, so that the effective state level of beneficial mineral elements in the compost products is improved, and the quality of the compost products is improved.

Drawings

FIG. 1 is a mineral profile of fly ash obtained by high temperature combustion.

Fig. 2 is an XRD pattern of mineral matter particles separated from coal or coal refuse used in the present invention before combustion or chemical conversion thereof.

FIG. 3 is a table of the mineral components of the mineral matter particles separated from the coal or coal refuse used in the present invention prior to combustion or chemical conversion thereof.

Fig. 4 shows the results of chemical component analysis of mineral particles separated from coal or coal refuse used in the present invention before combustion or chemical conversion, and is made by a certain neutral detection mechanism.

FIG. 5 is an industry standard screenshot of the heavy metal content of an organic fertilizer.

FIG. 6 is a graph showing the change of germination index with time during aerobic fermentative composting in example 1.

FIG. 7 is a graph showing the change of germination index with time during aerobic fermentative composting in example 2.

Detailed Description

Example 1

Taking corn straws, chicken manure and slurry-state decay-promoting and mature mineral particles as raw materials to ferment in an indoor 100L fermentation tank. Firstly, uniformly mixing the slurry-state decay-promoting and mature mineral substance granular minerals and corn straws, then adding a certain mass of chicken manure, and adjusting the carbon-nitrogen ratio to 42. Then, a fermentation broth (1L/fresh material) was added, and a suitable amount of water was further added to adjust the water content to about 60%. The control group (CK) was prepared without adding the staling-promoting mineral particles, test 1(T1) was prepared by adding 5% of the staling-promoting mineral particles (5% of the total fresh weight), and test 2(T2) was prepared by adding 10% of the staling-promoting mineral particles (10% of the total fresh weight). The fermentation period was 41 days. The nitrogen contents of the initial mixture and the fermentation decomposed product were measured as shown in table 1 below; and the germination index during fermentation and maturation was monitored as shown in fig. 5.

(1) Nitrogen content

TABLE 1 variation of nitrogen content during composting

Note: the nitrogen content after fermentation is increased because the quality of the material is significantly reduced as the fermentation progresses, and the value becomes larger as the denominator becomes smaller. Wherein the content of the first and second substances,

initial N (%): initial Material Nitrogen quantity/initial Material quantity

Final N (%): final nitrogen/final material quantity

The nitrogen loss rate was calculated as: (initial nitrogen amount-final nitrogen amount)/initial nitrogen amount), wherein:

initial nitrogen content ═ initial fermentation starting material amount [% initial nitrogen content ]

Final nitrogen content ═ final fermentation material content [% ]

As is clear from table 1, CK, T1, and T2 have nitrogen loss rates of 40.1%, 31.70%, and 31.00%, respectively, and T1 and T2 have lower nitrogen loss rates than CK, and thus it is known that the addition of these corrosion-promoting and ripening mineral particles to CK effectively reduces nitrogen loss and improves fertilizer quality.

(2) Index of germination

The germination index is a main index for representing whether the compost materials have toxic action on seeds or not so as to verify whether the materials are thoroughly decomposed or not. As can be seen from FIG. 1, both CK and T2 have a final germination index (GI >0.7) that is one of the indexes of maturity, and the trends of change are consistent. But there was a significant difference starting on day 12. T2 shows that proper addition of the decomposition promoting mineral particles can effectively accelerate the decomposition of the material when the material reaches one of the decomposition indexes at the beginning of 12 days.

Example 2

Rice chaff, pig manure and powdery corrosion-promoting and ripening mineral substance particles are used as raw materials to be fermented in an indoor 100L fermentation tank. Firstly, powdery corrosion-promoting and ripening mineral substance particles are uniformly mixed with rice chaff, then pig manure with certain mass is added, and the carbon-nitrogen ratio is adjusted to 35. Then, a fermentation broth (1L/fresh material) was added, and a suitable amount of water was further added to adjust the water content to about 60%. The control group (CK) was supplemented with no decomposition-promoting mineral particles, and test 1(T1) was supplemented with 10% decomposition-promoting mineral particles (10% of the total fresh weight of the material). The fermentation period was 50 days during which the germination index was monitored for changes, as shown in figure 7.

As can be seen from FIG. 2, the two trends are substantially consistent, and the germination index is increased with the progress of fermentation. In contrast, CK failed to meet the maturity index requirement at the end of fermentation, but T1 group reached the maturity requirement (GI >0.7) at 24 days of fermentation, indicating that proper addition of the maturity-promoting mineral particles can effectively accelerate material maturity.

Claims

1. A method for promoting the decomposition process of aerobic compost and improving the quality of the compost is characterized in that a mixture of organic materials and decomposition-promoting mineral particles is subjected to aerobic compost fermentation and decomposition, wherein the decomposition-promoting mineral particles comprise mineral particles separated from coal or coal gangue before combustion or chemical conversion, and the chemical conversion comprises coal pyrolysis, coal gasification, coal liquefaction, coal dry distillation or coal coking.

2. The method according to claim 1, wherein the organic material is selected from agricultural and forestry waste, food processing waste, animal wastes, algae, kitchen waste or any mixture thereof.

3. The process according to claim 1, wherein the mineral matter particles separated from the coal or coal refuse before combustion or chemical conversion are obtained by two means:

4. The method of claim 3, wherein the additive is a hydrophilic nanoparticle that is an aluminosilicate nanoparticle, a collector that is a non-polar hydrocarbon oil, or a surfactant that is a surface active molecule having a hydrophilic group and a hydrophobic group.

5. The method of claim 4, wherein the aluminosilicate nanoparticles are prepared by further grinding the mineral particles separated in step B to a nanoscale range; the collecting agent is kerosene, diesel oil or artificially synthesized nonpolar hydrocarbon oil; the surfactant is pinitol oil, camphor oil, phenolic acid mixed fatty alcohol, isomeric hexanol, octanol, ether alcohol or ester substances.

6. The process according to claim 1, wherein the mineral matter particles separated from the coal or coal refuse before combustion or chemical conversion are less than 100 μm in size and comprise kaolinite, illite, chlorite, quartz, pyrite, calcium carbonate and feldspar.

7. The method according to claim 1, wherein the moisture content of the mixture of organic material and humility-promoting mineral particles is adjusted to 50-70% and the humility-promoting mineral particles account for 2-20% of the mass of the mixture.

8. The method of claim 1, wherein the fermentation and decomposition comprises static aerobic composting fermentation in a stack, in a trough or in a reactor, and the fermentation process is light-shielding and heat-preserving, and the temperature in the high-temperature fermentation period is kept above 45 ℃.

9. The method of claim 1, wherein the fermentation and maturation is performed by fermentation using a microorganism species naturally present in the organic material, or by addition of a microorganism species selected from the group consisting of photosynthetic bacteria, lactic acid bacteria, yeast bacteria, gram-positive actinomycetes, and filamentous bacteria to the mixture.

10. The method of claim 1, wherein the organic material is organic material that has been subjected to different degrees of fermentation maturity; or carrying out secondary fermentation on the product obtained by the method of the invention.