Compound fertilizer production process

Abstract

The invention discloses a compound fertilizer production process, and belongs to the technical field of fertilizers, the compound fertilizer production process comprises the following steps: (1) mixing raw material components of a compound fertilizer, then adding citric acid, granulating in the presence of water vapor to obtain particles, and then sending the particles into drying equipment; (2) feeding coal-fired boiler tail gas into a drying machine, mixing the coal-fired boiler tail gas with the particulate matters in the step (1), and performing heat exchange to obtain a compound fertilizer; the compound fertilizer comprises the following raw material components: urea, ammonium dihydrogen phosphate, potassium salt, alginate oligosaccharide, chitosan oligosaccharide, compound acid, sodium alginate, trace elements and a corn straw extract. The compound acid comprises alanine and at least one of arginine, glycine and glutamic acid. The production process of the compound fertilizer not only reduces the treatment cost of coal combustion tail gas, but also has good fertilizer efficiency and increases the yield of crops.

Description

Technical Field

[0001] The present invention belongs to the technical field of fertilizers, and particularly relates to a production process of compound fertilizers. Background Art

[0002] During the production process of compound fertilizers, it is necessary to dry the granules to reduce the granule moisture to the lowest level, avoid granule pulverization due to moisture during storage, and improve granule strength. The main heat source during the drying of compound fertilizers comes from coal combustion. Coal contains a certain amount of sulfur and nitrogen, which react with oxygen in the air during combustion to generate air pollutants, mainly sulfur dioxide, hydrogen sulfide, nitrogen monoxide, etc. The sulfur oxides in the waste gas have a corrosive effect on metal structural parts, bringing certain difficulties to the selection of dust collectors. The commonly used desulfurization and denitrification technology is to contact the tail gas after coal combustion with a sprayed acid-base solution for neutralization, so as to achieve the purpose of desulfurization and denitrification. However, this desulfurization and denitrification process requires a large amount of capital to build equipment, recovery ponds, etc., wastes the heat of the coal combustion tail gas, and greatly increases the tail gas treatment cost.

[0003] Sulfur is an important component of cystine, cysteine and methionine, and participates in the formation of chlorophyll; it plays an important role in the formation and activation of certain enzymes in plants; sulfur can increase the cold resistance and drought resistance of certain crops. Whether crops lack sulfur or nitrogen, it will affect their normal growth and lead to a decrease in both yield and quality.

[0004] Therefore, there is an urgent need to provide a new production method for compound fertilizers, which not only reduces the cost of treating coal combustion tail gas, but also has good fertilizer efficiency and increases the yield of crops. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above prior art. For this purpose, the present invention provides a production process of compound fertilizers. The production process of compound fertilizers according to the present invention not only reduces the cost of treating coal combustion tail gas, but also has good fertilizer efficiency and increases the yield of crops.

[0006] In order to solve the air pollutants generated during the coal drying process, while ensuring the heat supply and reducing unnecessary economic investment. The present invention provides a production process of compound fertilizers, which can not only improve the fertilizer efficiency of compound fertilizers, but also save energy, reduce emissions and eliminate pollution.

[0007] A production process of compound fertilizers includes the following steps: (1) Mix the raw material components of the compound fertilizer, then add citric acid, and granulate under the condition of the presence of water vapor to obtain granules, and then send them to a drying device; (2) Send the tail gas of the coal-fired boiler into the dryer, and mix and exchange heat the tail gas of the coal-fired boiler with the granules in step (1) to obtain compound fertilizers; The raw material components of the compound fertilizer include urea, ammonium dihydrogen phosphate, potassium salt, fucoidan oligosaccharide, chitosan oligosaccharide, compound acid, sodium alginate, trace elements, and corn straw extract; The preparation method of the corn straw extract includes: drying, slicing, and pulverizing corn straw and matsutake respectively, then mixing them, adding water and cellulase, stirring, performing enzymatic hydrolysis, then extracting in a boiling water bath, then performing ultrasonic extraction, filtering, collecting the filtrate, concentrating under reduced pressure, drying, and pulverizing to obtain the corn straw extract; The compound acid includes alanine and at least one of arginine, glycine, and glutamic acid.

[0008] Preferably, in the compound acid, the weight ratio of alanine to at least one of arginine, glycine, and glutamic acid is 1:(0.5 - 1.2), and more preferably 1:(0.8 - 1).

[0009] Preferably, the weight ratio of the corn straw to matsutake is 100:(1 - 5), and more preferably 100:(2 - 4).

[0010] Preferably, it is pulverized to a particle size less than 1 cm, and more preferably 2 mm - 8 mm.

[0011] Preferably, the temperature of the enzymatic hydrolysis is 35 - 45°C, and the time of the enzymatic hydrolysis is 3 - 6 hours.

[0012] Preferably, the addition amount of the cellulase is 2% - 7% of the weight of the pulverized corn straw, and more preferably 3% - 6%.

[0013] Preferably, the unit enzyme activity of the cellulase is 90 - 100 U / mg. For example, it is 100 U / mg.

[0014] Preferably, the weight of the water is 50% - 100% of the weight of the pulverized corn straw, and more preferably 80% - 100%.

[0015] Preferably, the extraction time in the boiling water bath is 20 - 40 minutes. For example, it is 30 minutes or 40 minutes.

[0016] Preferably, the temperature of the ultrasonic extraction is 70 - 75°C, and the time is 30 - 60 minutes. More preferably, the temperature of the ultrasonic extraction is 70 - 72°C, and the time is 45 - 50 minutes.

[0017] Preferably, the frequency of the ultrasonic wave is 60 - 80 kHz, and the power is 100 - 200 W.

[0018] Preferably, the processes of reduced-pressure concentration, drying, and pulverization are carried out under the conditions of 45 - 55°C and -0.1 to -0.2 MPa. The raw water is concentrated under reduced pressure to 1 / 6 - 1 / 10 of its original volume to obtain a concentrate, and then the concentrate is dried under vacuum at 60 - 80°C and -0.1 to -0.2 MPa and pulverized to obtain the corn straw extract.

[0019] Preferably, the potassium salt includes at least one of potassium sulfate or potassium nitrate.

[0020] Preferably, the trace elements include at least one of zinc, iron, manganese, and copper. These trace elements can participate in the synthesis of plant enzymes and proteins, promote plant photosynthesis, and thus increase the yield of plant fruits.

[0021] Preferably, the trace elements are provided by at least one of nitrates and sulfates of zinc, iron, manganese, and copper.

[0022] Preferably, the raw material components of the compound fertilizer, by weight, include 40 parts of urea, 5 - 10 parts of ammonium dihydrogen phosphate, 5 - 10 parts of potassium salt, 1 - 4 parts of fucoidan oligosaccharide, 2 - 6 parts of chitosan oligosaccharide, 1 - 5 parts of compound acid, 2 - 8 parts of sodium alginate, 0.5 - 3 parts of trace elements, and 0.5 - 3 parts of corn straw extract; more preferably, the raw material components of the compound fertilizer, by weight, include 40 parts of urea, 6 - 8 parts of ammonium dihydrogen phosphate, 5 - 8 parts of potassium salt, 2 - 4 parts of fucoidan oligosaccharide, 3 - 5 parts of chitosan oligosaccharide, 2 - 5 parts of compound acid, 3 - 8 parts of sodium alginate, 1 - 2 parts of trace elements, and 1 - 3 parts of corn straw extract.

[0023] Preferably, the weight of citric acid is 0.1% - 1% of the total weight of the raw material components of the compound fertilizer, and more preferably 0.5% - 0.8%.

[0024] Preferably, the absorbed tail gas undergoes cyclone dust removal, sedimentation dust removal, water washing dust removal, and water film water removal, and finally meets the emission standards for discharge.

[0025] Preferably, the compound acid further includes humic acid. The combination of humic acid with alanine and at least one of arginine, glycine, and glutamic acid can not only greatly improve the disease resistance of plants, but also help increase the plant yield.

[0026] Preferably, the particle diameter of the compound fertilizer is 1 - 3 mm, the density of the compound fertilizer is 1.1 - 1.2 g / m 3 and the specific surface area is 65,000 - 70,000 m 2 .

[0027] Approximately 15.0 - 16.5 kg of coal is consumed for drying one ton of compound fertilizer. The equipment production capacity is 18 - 20 t / h. During the drying process, the drying furnace burns 300 - 330 kg of coal per hour. After burning one ton of coal, approximately 15 - 16 kg of sulfur dioxide is generated. The drying equipment produces 4 - 5.28 kg of sulfur dioxide per hour.

[0028] Citric acid is added to each raw material component of the compound fertilizer. After mixing and stirring, it is sent into a granulator and undergoes drum granulation in the presence of steam. At this time, under the action of steam, citric acid participates in the granulation of the compound fertilizer, adsorbs on the surface of the particulate matter, and the wet particulate matter is sent to a dryer. The tail gas of the coal-fired boiler is sent into the dryer. The wet particulate matter is fully mixed and heat-exchanged with the tail gas of the coal-fired boiler under the action of the baffle. At this time, a citrate solution is formed on the surface of the wet particulate matter, which absorbs gases such as sulfur dioxide and nitrogen oxides in the tail gas. Sulfur dioxide reacts with water to form sulfurous acid, which turns into sulfuric acid under heating conditions. Sulfuric acid reacts with citrate; achieving the effect of treating the tail gas. Excessive citric acid and citrate have very strong complexing abilities, complex with metal ions to form soluble citrates, which can improve the fertilizer efficiency.

[0029] The particulate matter with a wet surface forms an absorption curtain under the action of the rotation of the dryer and the baffle, fully absorbing the tail gas of the coal-fired boiler. The absorbed tail gas undergoes cyclone dust removal, sedimentation dust removal, water washing dust removal, and water film dewatering, and finally reaches the standard for discharge. The absorbed particulate matter enters the finished product packaging after the post-treatment process of the compound fertilizer.

[0030] A compound fertilizer is prepared by the above compound fertilizer production process.

[0031] Application of the above compound fertilizer production process in plant cultivation.

[0032] Preferably, the plants include corn, wheat, soybeans, and tomatoes.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Each raw material component of the compound fertilizer of the present invention includes urea, ammonium dihydrogen phosphate, potassium salt, fucoidan oligosaccharide, chitosan oligosaccharide, compound acid, sodium alginate, trace elements, and corn straw extract; through fucoidan oligosaccharide, chitosan oligosaccharide, compound acid, sodium alginate, trace elements, and corn straw extract, and then in combination with urea, ammonium dihydrogen phosphate, and potassium salt, the nutrient components during the growth process of plants or plants are guaranteed. The preparation process of the corn straw extract introduces a small amount of Tricholoma matsutake, which is beneficial to stimulating the rapid growth of plants and increasing the weight of plant fruits. The mutual cooperation between fucoidan oligosaccharide, chitosan oligosaccharide, and compound acid is also beneficial to the growth and yield improvement of plants, such as corn.

[0034] (2) The composite acid also includes humic acid. The combination of humic acid with alanine and at least one of arginine, glycine, and glutamic acid can not only greatly improve the disease resistance of plants, but also help increase the plant yield.

[0035] (3) The compound fertilizer of the present invention can adjust the acidity and alkalinity of the soil, increase the content of soil organic matter, and protect and improve the soil quality.

[0036] (4) Citric acid is economically affordable, with sufficient market supply and demand, easy-to-obtain raw materials, which can improve the plant growth environment, promote well-developed roots, enhance disease resistance, increase crop yield, and improve product quality.

[0037] (5) The production process of the present invention absorbs sulfur and nitrate in the tail gas, converts them into nutrients in the fertilizer, avoids air pollution, and can also make full use of the heat in the tail gas, playing the role of turning waste into treasure.

[0038] (6) The tail gas desulfurization and denitrification process is simple and easy to operate, reducing the production cost of the product and being beneficial to the competitiveness of the product in the market. Specific Embodiments

[0039] In order to make those skilled in the art more clearly understand the technical solution of the present invention, the following examples are listed for illustration. It should be noted that the following examples do not limit the scope of protection required by the present invention.

[0040] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial channels or can be obtained by existing known methods.

[0041] Example 1 A compound fertilizer production process includes the following steps: (1) Mix the raw material components of the compound fertilizer, then add 0.5% of citric acid based on the total weight of the raw material components of the compound fertilizer. After mixing and stirring, it is sent into a granulator, and drum granulation is carried out under the condition of the presence of water vapor to obtain particulate matter, and then it is sent to a dryer; (2) Send the tail gas of the coal-fired boiler into the dryer. Under the action of the baffle, the tail gas of the coal-fired boiler is mixed with the particulate matter in step (1) and heat-exchanged for 2 hours to obtain the compound fertilizer; The raw material components of the compound fertilizer, by weight, include 40 parts of urea, 6 parts of ammonium dihydrogen phosphate, 7 parts of potassium nitrate, 3 parts of fucoidan oligosaccharide, 4 parts of chitosan oligosaccharide, 4 parts of composite acid, 5 parts of sodium alginate, 1 part of trace elements (the trace elements are composed of zinc nitrate, iron nitrate, manganese nitrate, and copper nitrate in a weight ratio of 2:1:1:1), and 2 parts of corn straw extract; The composite acid includes alanine and arginine, glycine, and the weight ratio of alanine, arginine, and glycine is 1:0.4:0.4; The preparation method of corn straw extract includes: drying corn straw and Tricholoma matsutake at 90 °C for 3 hours respectively, slicing and crushing them to a particle size less than 1 cm, then mixing for 30 minutes, with the weight ratio of corn straw to Tricholoma matsutake being 100:2. Then add water and cellulase. The weight of water is 80% of the weight of the crushed corn straw, and the addition amount of cellulase is 3% of the weight of the crushed corn straw. The unit enzyme activity of cellulase is 100 U / mg. Stir and carry out enzymatic hydrolysis at a temperature of 40 °C for 5 hours. Then extract in a boiling water bath for 30 minutes, and then carry out ultrasonic extraction at a temperature of 70 °C for 40 minutes. The frequency of ultrasonic wave is 60 kHz and the power is 100 W. Filter and collect the filtrate, and concentrate it under reduced pressure to 1 / 10 of the original volume at 50 °C and -0.1 MPa to obtain a concentrate. Then vacuum-dry the concentrate at 80 °C and -0.1 MPa and crush it to obtain corn straw extract.

[0042] The absorbed tail gas passes through cyclone dust removal, sedimentation dust removal, water washing dust removal and water film water removal, and finally reaches the discharge standard for emission.

[0043] Example 2 A compound fertilizer production process includes the following steps: (1) Mix each raw material component of the compound fertilizer, then add 0.6% of citric acid based on the total weight of each raw material component of the compound fertilizer. After mixing and stirring, send it into a granulator and carry out rotary drum granulation in the presence of water vapor to obtain particulate matter, and then send it to a dryer; (2) Send the tail gas of a coal-fired boiler into the dryer. Under the action of a baffle, the tail gas of the coal-fired boiler is mixed with the particulate matter in step (1) and heat-exchanged for 1.5 hours to obtain compound fertilizer; Each raw material component of the compound fertilizer, by weight, includes 40 parts of urea, 5 parts of ammonium dihydrogen phosphate, 5 parts of potassium nitrate, 4 parts of fucoidan oligosaccharide, 5 parts of chitosan oligosaccharide, 3 parts of compound acid, 4 parts of sodium alginate, 1 part of trace elements (the trace elements are composed of zinc nitrate, iron nitrate, manganese nitrate, copper nitrate in a weight ratio of 2.5:0.5:1:1) and 2.5 parts of corn straw extract; The compound acid includes alanine, as well as arginine, glycine, glutamic acid, and the weight ratio of alanine, arginine, glycine, glutamic acid is 1:0.3:0.4:0.3; The preparation method of corn straw extract includes: drying corn straw and Tricholoma matsutake at 90°C for 3 hours respectively, slicing and crushing them to a particle size less than 1 cm, then mixing for 30 minutes with the weight ratio of corn straw to Tricholoma matsutake being 100:1, adding water and cellulase. The weight of water is 70% of the weight of the crushed corn straw, and the addition amount of cellulase is 4% of the weight of the crushed corn straw. The unit enzyme activity of cellulase is 100 U / mg. Stir and carry out enzymatic hydrolysis at a temperature of 45°C for 5 hours, then extract in a boiling water bath for 30 minutes, and then carry out ultrasonic extraction at a temperature of 70°C for 40 minutes. The frequency of ultrasonic wave is 60 kHz and the power is 100 W. Filter and collect the filtrate, concentrate it under reduced pressure to 1 / 10 of the original volume at 50°C and -0.1 MPa to obtain a concentrate, and then vacuum dry the concentrate at 80°C and -0.1 MPa and crush it to obtain corn straw extract.

[0044] The exhausted gas after absorption undergoes cyclone dust removal, sedimentation dust removal, water washing dust removal and water film water removal, and finally reaches the discharge standard.

[0045] Example 3 A compound fertilizer production process includes the following steps: (1) Mix each raw material component of the compound fertilizer, then add 0.5% of citric acid based on the total weight of each raw material component of the compound fertilizer, send it to a granulator after mixing and stirring, and carry out drum granulation in the presence of water vapor to obtain particulate matter, and then send it to a dryer; (2) Send the tail gas of the coal-fired boiler to the dryer, and under the action of the baffle, mix and exchange heat between the tail gas of the coal-fired boiler and the particulate matter in step (1) for 2 hours to obtain compound fertilizer; Each raw material component of the compound fertilizer, by weight, includes 40 parts of urea, 6 parts of ammonium dihydrogen phosphate, 7 parts of potassium nitrate, 3 parts of fucoidan oligosaccharide, 4 parts of chitosan oligosaccharide, 5 parts of compound acid, 5 parts of sodium alginate, 1 part of trace elements (the trace elements are composed of zinc nitrate, iron nitrate, manganese nitrate, copper nitrate according to the weight ratio of 2:1:1:1) and 2 parts of corn straw extract; The compound acid includes humic acid, alanine, as well as arginine and glycine, and the weight ratio of humic acid, alanine, arginine and glycine is 1:1:0.4:0.4; The preparation method of corn straw extract includes: drying corn straw and Tricholoma matsutake at 90°C for 3 hours respectively, slicing and pulverizing them to a particle size less than 1 cm, then mixing for 30 minutes. The weight ratio of corn straw to Tricholoma matsutake is 100:2. Then add water and cellulase. The weight of water is 80% of the weight of the pulverized corn straw, and the addition amount of cellulase is 3% of the weight of the pulverized corn straw. The unit enzyme activity of cellulase is 100 U / mg. Stir and carry out enzymatic hydrolysis. The temperature of enzymatic hydrolysis is 40°C and the time is 5 hours. Then extract in a boiling water bath for 30 minutes, and then carry out ultrasonic extraction. The temperature of ultrasonic extraction is 70°C, the time is 40 minutes, the frequency of ultrasonic wave is 60 kHz, and the power is 100 W. Filter and collect the filtrate, and concentrate it under reduced pressure to 1 / 10 of the original volume at 50°C and -0.1 MPa to obtain a concentrate. Then vacuum-dry the concentrate at 80°C and -0.1 MPa, and pulverize it to obtain corn straw extract.

[0046] The exhausted gas after absorption is subjected to cyclone dust removal, sedimentation dust removal, water washing dust removal and water film water removal, and finally reaches the discharge standard.

[0047] Comparative Example 1 Compared with Example 1, the difference in Comparative Example 1 is only that citric acid is not added, and other processes are the same as those in Example 1.

[0048] Comparative Example 2 Compared with Example 1, the difference in Comparative Example 2 is only that alanine is replaced with an equal amount of arginine, and other processes are the same as those in Example 1.

[0049] Comparative Example 3 Compared with Example 1, the difference in Comparative Example 3 is only that Tricholoma matsutake is replaced with an equal amount of corn straw, and other processes are the same as those in Example 1.

[0050] Product effect test 1. Corn planting experiment

[0051] Fertilizer effect tests were carried out on the compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-3. Corn was selected as the experimental crop. The row spacing for planting was about 70 cm and the plant spacing was about 30 cm. The same planting area and field management were adopted. The compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 were used as base fertilizers respectively, and the fertilization amount was 45 kg / mu. After harvesting the corn, the calculated emergence rate and corn yield (the calculation method of corn yield is yield per mu (kg) = number of ears per mu × number of grains per ear / number of grains per kg) were statistically calculated as shown in Table 1.

[0052] Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Emergence rate (%) 90 88 94 86 85 78 Maize yield per mu (kg) 678.2 665.4 698.6 642.7 635.8 563.1

[0053] As can be seen from Table 1, the fertilizer efficiency of the compound fertilizers prepared in Examples 1-3 is significantly better than that in Comparative Examples 1-3. From Examples 1 and Comparative Examples 1-3, it can be seen that the addition of citric acid can increase the fertilizer efficiency of the compound fertilizer, and the specific types of compound acids have an obvious promoting effect on the growth of corn. Also, during the preparation of corn straw extract, the addition of Tricholoma matsutake can promote the growth of corn and increase the yield. The reason may be that the Tricholoma matsutake extract is beneficial to stimulating the emergence of corn and increasing the yield.

[0054] 2. Wheat planting experiment Divide a one-acre experimental field into six equal parts. Take Yangguang 818 wheat as the experimental crop. Before sowing, plow the land. Apply the compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 to each plot, with 4.5 kg of compound fertilizer applied to each plot. The wheat sowing rate for each plot is 1 kg. When the wheat grows to the green-recovery stage, apply 4 kg of compound fertilizer to each plot again, and when it reaches the heading stage, apply 8 kg of compound fertilizer to each plot again. At the final maturity, collect the grains, weigh them, and count the wheat yield and the morphology of wheat grains in each plot. The results are shown in Table 2 below.

[0055] Table 2 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Yield (kg) 125.3 116.6 139.7 108.2 101.1 94.6 Morphology of wheat grains Full grains Full grains Full grains Full grains Full grains Full grains

[0056] As can be seen from Table 2, the compound fertilizers prepared in the embodiments of the present invention have better fertilizer efficiency in wheat planting. It is further proved that during the production process of the compound fertilizer of the present invention, the addition of citric acid can increase the fertilizer efficiency of the compound fertilizer, the specific types of compound acids have an obvious promoting effect on the growth of wheat, and during the preparation of corn straw extract, the addition of Tricholoma matsutake can promote the increase of wheat yield.

[0057] It should be noted that in this article, terms such as "including, containing" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0058] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A compound fertilizer production process, characterized in that, It includes the following steps: (1) Mix the raw material components of the compound fertilizer, then add citric acid, granulate under the condition of the presence of water vapor to obtain particulate matter, and then send it to a drying device; (2) Send the tail gas of the coal-fired boiler into the dryer, and mix and heat exchange the tail gas of the coal-fired boiler with the particulate matter in step (1) to obtain the compound fertilizer; The raw material components of the compound fertilizer include urea, ammonium dihydrogen phosphate, potassium salt, fucoidan oligosaccharide, chitosan oligosaccharide, compound acid, sodium alginate, trace elements and corn straw extract; The preparation method of the corn straw extract includes: drying, slicing and pulverizing corn straw and matsutake respectively, then mixing, adding water and cellulase, stirring, performing enzymatic hydrolysis, then extracting in a boiling water bath, then performing ultrasonic extraction, filtering, collecting the filtrate, concentrating under reduced pressure, drying, and pulverizing to obtain the corn straw extract; The compound acid includes alanine and at least one of arginine, glycine and glutamic acid.

2. The compound fertilizer production process according to claim 1, characterized in that, The weight ratio of the corn straw to the matsutake is 100:(1-5).

3. The compound fertilizer production process according to claim 1, wherein The temperature of the enzymatic hydrolysis is 35-45°C, and the time of the enzymatic hydrolysis is 3-6 hours.

4. The compound fertilizer production process according to claim 1, characterized in that, The extraction time in the boiling water bath is 20-40 minutes; and / or, the temperature of the ultrasonic extraction is 70-75°C, and the time is 30-60 minutes.

5. The compound fertilizer production process according to claim 1, characterized in that, The potassium salt includes at least one of potassium sulfate or potassium nitrate.

6. The compound fertilizer production process according to claim 1, characterized in that, The trace elements include at least one of zinc, iron, manganese and copper.

7. The compound fertilizer production process according to claim 1, wherein The raw material components of the compound fertilizer, by weight, include 40 parts of urea, 5-10 parts of ammonium dihydrogen phosphate, 5-10 parts of potassium salt, 1-4 parts of fucoidan oligosaccharide, 2-6 parts of chitosan oligosaccharide, 1-5 parts of compound acid, 2-8 parts of sodium alginate, 0.5-3 parts of trace elements and 0.5-3 parts of corn straw extract.

8. The compound fertilizer production process according to any one of claims 1-7, characterized in that, The weight of the citric acid is 0.1% to 1% of the total weight of the raw material components of the compound fertilizer.

9. A compound fertilizer, characterized in that, Prepared by the compound fertilizer production process according to any one of claims 1-8.

10. Application of the compound fertilizer production process according to any one of claims 1-8 in plant cultivation.