Specialized sulfur-based compound fertilizer for leafy vegetables, preparation method and device

Abstract

The application discloses a kind of special sulfur-based compound fertilizer of leaf vegetable, preparation method and device, belong to compound fertilizer preparation technical field.The preparation of the compound fertilizer includes the following steps: sulfur, anhydrous ethanol are mixed and stirred, constant temperature oscillation, stand until clear state, take supernatant and mix with distilled water, oscillation, add sodium dodecyl sulfate, oscillation, add coating agent, oscillation, obtain material B, stand by;Ammonia is introduced into phosphoric acid to adjust to pH 4.3-4.8, filter pressing, collect filtrate to obtain feed liquid D;Material B is filtered, and the filter residue is collected and mixed with feed liquid D, guar gum and locust bean gum are added, oscillation is carried out, a mixed slurry is obtained, granulation is carried out, drying is carried out, screening is carried out, and cooling is carried out, to obtain the compound fertilizer, improve the sulfur and phosphorus ammonium slurry combination degree, avoid the loss of fertilizer efficiency, prevent the occurrence of safety hazards.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of compound fertilizer preparation, and particularly relates to a leaf vegetable special sulfur-based compound fertilizer, a preparation method and a device. BACKGROUND

[0002] Leaf vegetables refer to vegetables whose edible parts are mainly leaves. Common leaf vegetables include Chinese cabbage, spinach, Chinese flowering cabbage, chives and lettuce. Leaf vegetables are rich in vitamins, folic acid, calcium and other nutrients, which can help to enhance immunity and promote bone health, and have the effects of diuresis, lung moistening and inflammation reduction, and are very beneficial to human health.

[0003] Sulfur is an important component of the structure of chlorophyll molecules, and chlorophyll is a key pigment for photosynthesis, which can absorb light energy and convert it into chemical energy required by plants. The application of sulfur fertilizer can provide sufficient sulfur element supply, which is beneficial to the synthesis of chlorophyll and the performance of photosynthesis, thereby promoting the growth of leaf vegetables and the formation of green leaves. Proper application of sulfur fertilizer can improve the absorption efficiency of plants to key nutrients such as nitrogen and phosphorus, thereby increasing the growth rate and yield of vegetables. Sulfur also has certain insecticidal and antibacterial effects, so fertilizers containing elemental sulfur are increasingly favored by growers.

[0004] Sulfur-phosphorus-ammonium fertilizer made of elemental sulfur as the elemental raw material can be directly applied or used as an additive of sulfur-based compound fertilizer. The sulfur source in sulfur-phosphorus-ammonium fertilizer mainly includes two types: one is elemental sulfur yellow, and the other is sulfur trioxide in sulfuric acid. Current sulfur-phosphorus-ammonium fertilizer mainly uses sulfur trioxide as the sulfur source, but the effect of sulfur trioxide in the soil is short in time, and the absorption amount of crops is limited. A small part of the sulfur source of sulfur-phosphorus-ammonium fertilizer is granular sulfur yellow.

[0005] However, since sulfur yellow is insoluble in water and most organic solvents, it is difficult to combine sulfur yellow and phosphorus-ammonium slurry, and the phosphorus-ammonium slurry cannot completely cover the sulfur yellow. In the granulation and drying process, the poor combination and the volatilization of water cause the sulfur yellow powder to seep out, which reduces the fertilizer efficiency on the one hand, and on the other hand, the dry sulfur yellow powder floats in the air to form an explosive mixture, which is easy to be ignited by static electricity to cause dust explosion, and has safety hazards. SUMMARY

[0006] The application discloses a kind of special sulfur-based compound fertilizer of leaf vegetable, preparation method and device, belong to compound fertilizer preparation technical field.The preparation of the compound fertilizer includes the following steps: sulfur, anhydrous ethanol are mixed and stirred, constant temperature oscillation, stand until clear, take supernatant and mix with distilled water, oscillation, add sodium dodecyl sulfate, oscillation, add coating agent, oscillation, obtain material B, stand by;Ammonia is introduced into phosphoric acid to adjust pH to 4.3-4.8, filter pressing, collect filtrate to obtain feed liquid D;Material B is filtered, and the filter residue is mixed with feed liquid D, guar gum and locust bean gum are added, oscillation, to obtain mixed slurry, granulation, drying, screening, cooling, to obtain the compound fertilizer.

[0007] The technical problem to be solved by the application is to improve the combination degree of sulfur and ammonium phosphate slurry, avoid loss of fertilizer efficiency, and prevent safety hazards.

[0008] The object of the application can be achieved by the following technical solutions.

[0009] A preparation method of a special sulfur-based compound fertilizer for leaf vegetables, the preparation of the compound fertilizer includes the following steps:

[0010] (1) sulfur, anhydrous ethanol are mixed and stirred in a material tank, stirred for 4-6 h, heated to 60°C, constant temperature oscillation for 0.5-1 h, to obtain material A;

[0011] (2) the material A is stood until clear, the supernatant is placed in a processing tank, distilled water is added for mixing, oscillation for 1-2 h, sodium dodecyl sulfate is added, oscillation for 1-2 h, a coating agent is added to the processing tank, oscillation for 30-40 min, to obtain material B, stand by;

[0012] (3) phosphoric acid is placed in a reaction kettle, heated to 60°C, ammonia is introduced under constant temperature conditions to adjust pH to 4.3-4.8, to obtain slurry C, the slurry C is introduced into a filter press for filter pressing, the filtrate is collected and placed in a mixing kettle, to obtain feed liquid D;

[0013] (4) material B is filtered, the filter residue is collected, and then the filter residue is introduced into the mixing kettle and mixed with the feed liquid D, guar gum and locust bean gum are added to the mixing kettle, oscillation for 25-40 min, to obtain mixed slurry;

[0014] (5) the mixed slurry is introduced into a granulator for granulation, the granulated material is introduced into a dryer for drying, the dried material is screened by a vibrating screen, to obtain qualified particles with a particle size of 3-5 mm, and the qualified particles are introduced into a cooler for cooling, to obtain the compound fertilizer; the water content of the dried material is less than 1.5%.

[0015] As a preferred technical scheme of the present application, in step (1), the amount of sulfur and anhydrous ethanol is 500g:2-3L.

[0016] As a preferred technical scheme of the present application, in step (2), the amount of the supernatant, distilled water, sodium dodecyl sulfate and coating agent is 1L:2-3L:5-8g:100-200g.

[0017] As a preferred technical scheme of the present application, in step (3), the pressure filtration refers to pressure maintaining for 10-20min under a pressure of 40-50MPa.

[0018] As a preferred technical scheme of the present application, in step (4), the mass ratio of the filter residue, feed liquid D, guar gum and locust bean gum is 500:1200-2200:100-200:80-100.

[0019] As a preferred technical scheme of the present application, the coating agent is a porous degradable material.

[0020] As a preferred technical scheme of the present application, the preparation of the coating agent comprises the following steps:

[0021] S1, mix tripartite gum and deionized water, stir for 20-30min, filter, and obtain material E from the liquid phase;

[0022] S2, mix zein and ethanol aqueous solution, stir for 30-40min, and obtain material F;

[0023] S3, mix the material E and the material F, add calcium polyphosphate, stir for 6-8h, obtain a mixed liquid G, transfer the mixed liquid G to a forming mold, stand for 12-18h, freeze at-15~-20℃ for 20-24h, and dry under a vacuum condition of 150-180Pa for 2-3h, and obtain the coating agent.

[0024] As a preferred technical scheme of the present application, in step S1, the amount of tripartite gum and deionized water is 1-2g:100-200mL; in step S2, the amount of zein and ethanol aqueous solution is 3-4g:100-120mL, and the volume fraction of ethanol in the ethanol aqueous solution is 85%; in step S3, the amount of the material E, the material F and calcium polyphosphate is 10-20mL:8-10mL:3-4g.

[0025] A leaf vegetable special sulfur-based compound fertilizer prepared by the above preparation method.

[0026] The application discloses a device for preparing a special sulfur-based compound fertilizer for leaf vegetables.

[0027] The material tank is connected with the processing tank.

[0028] The processing tank is provided with a filter screen, and the processing tank conveys filter residues obtained after the filter screen to the mixing kettle.

[0029] The input end of the reaction kettle is connected with the output end of the ammonia gas storage tank, and the output end of the reaction kettle is connected with the input end of the filter press.

[0030] The output end of the filter press is connected with the input end of the mixing kettle.

[0031] The output end of the mixing kettle is connected with the input end of the granulator.

[0032] The output end of the granulator is connected with the input end of the dryer.

[0033] The output end of the dryer is connected with the input end of the vibrating screen.

[0034] The output end of the vibrating screen is connected with the input end of the cooler.

[0035] The output end of the cooler is connected with the input end of the packaging machine.

[0036] The output end of the packaging machine outputs the packaged compound fertilizer.

[0037] The application has the following beneficial effects:

[0038] The application discloses a special sulfur-based compound fertilizer for leaf vegetables, a preparation method and a device. The sulfur powder is made into sol, and sodium dodecyl sulfate is added to make the sulfur powder uniformly and stably dispersed and avoid agglomeration, so that the prepared compound fertilizer has uniform particle size. After the sulfur sol is coated with a coating agent and mixed with the ammonium phosphate slurry, the combination degree of the sulfur powder and the ammonium phosphate slurry is increased by the adhesion of the triazine glue in the coating agent and the synergistic effect of the guar gum and locust bean gum, so that the sulfur powder is difficult to expose and maintain the fertilizer efficiency. Meanwhile, the sulfur powder is prevented from directly contacting with air in the drying process, and the production risk is eliminated. DETAILED DESCRIPTION

[0039] In order to further illustrate the technical means and effects adopted by the application to achieve the predetermined application purposes, the specific embodiments, structures, features and effects according to the application are described in detail as follows in combination with the embodiments.

[0040] Embodiment 1

[0041] The preparation of the compound fertilizer comprises the following steps:

[0042] (1) Put sulfur and anhydrous ethanol into a material tank and mix, stir for 4 h, heat to 60℃ constant temperature oscillation for 0.5 h, to obtain material A; the amount ratio of sulfur and anhydrous ethanol is 500 g:2 L;

[0043] (2) Let the material A stand to a clear state, take the supernatant and put it into a processing tank, mix with distilled water, oscillate for 1 h, add sodium dodecyl sulfate, oscillate for 1 h, add a coating agent to the processing tank, oscillate for 30 min, to obtain material B, stand by;

[0044] The amount ratio of the supernatant, distilled water, sodium dodecyl sulfate and coating agent is 1 L:2 L:5 g:100 g;

[0045] (3) Put phosphoric acid into a reaction kettle, heat to 60℃ constant temperature, and pass in ammonia gas to adjust the pH to 4.3, to obtain slurry C, pass the slurry C into a filter press, collect the filtrate and put it into a mixing kettle, to obtain liquid D;

[0046] The pressure filtration refers to pressure keeping for 10 min under 40 MPa pressure;

[0047] (4) Take the material B to filter, collect the residue, then put the residue into the mixing kettle to mix with the liquid D, add guar gum and locust bean gum to the mixing kettle, oscillate for 25 min, to obtain mixed slurry;

[0048] The mass ratio of the residue, liquid D, guar gum and locust bean gum is 500:1200:100:80;

[0049] (5) Guide the mixed slurry into a granulator to granulate, the granulated material enters a dryer to dry, the dried material is screened through a vibrating screen to obtain qualified particles with a particle size of 3 mm, guide the qualified particles into a cooler to cool, to obtain the compound fertilizer; the water content of the dried material is less than 1.5%.

[0050] The preparation of the coating agent comprises the following steps:

[0051] S1, mix tri-sodium citrate and deionized water, stir for 20 min, filter, take the liquid phase to obtain material E; the amount ratio of tri-sodium citrate and deionized water is 1 g:100 mL;

[0052] S2, mix zein and ethanol aqueous solution, stir for 30 min, to obtain material F; the amount ratio of zein and ethanol aqueous solution is 3 g:100 mL; the volume fraction of ethanol in the ethanol aqueous solution is 85%;

[0053] S3, mixing the material E and the material F, adding calcium polyphosphate, stirring for 6h, to obtain a mixed solution G, transferring the mixed solution G to a forming mold, standing for 12h, freezing at-15℃ for 20h, drying under a vacuum condition of 150Pa for 2h, to obtain the coating agent; the dosing ratio of the material E, the material F and the calcium polyphosphate is 10mL:8mL:3g.

[0054] Example 2

[0055] The preparation of the compound fertilizer comprises the following steps:

[0056] (1) mixing sulfur and anhydrous ethanol in a material tank, stirring for 5h, heating to 60℃ and constant temperature oscillation for 0.8h, to obtain a material A; the dosing ratio of the sulfur and the anhydrous ethanol is 500g:2.5L;

[0057] (2) standing the material A to a clear state, taking the clear solution and placing it in a processing tank, mixing with distilled water, oscillating for 1.5h, adding sodium dodecyl sulfate, oscillating for 1.5h, adding a coating agent to the processing tank, oscillating for 35min, to obtain a material B, standing for use;

[0058] The dosing ratio of the clear solution, the distilled water, the sodium dodecyl sulfate and the coating agent is 1L:2.5L:7g:150g;

[0059] (3) placing phosphoric acid in a reaction kettle, heating to 60℃ under constant temperature conditions, and passing in ammonia gas to adjust the pH to 4.5, to obtain a slurry C, passing the slurry C into a filter press for pressure filtration, collecting the filtrate and placing it in a mixing kettle, to obtain a liquid D;

[0060] The pressure filtration refers to pressure maintaining for 15min under a pressure of 45MPa;

[0061] (4) filtering the material B, collecting the filter residue, and then placing the filter residue in the mixing kettle to mix with the liquid D, adding guar gum and locust bean gum to the mixing kettle, oscillating for 35min, to obtain a mixed slurry;

[0062] The mass ratio of the filter residue, the liquid D, the guar gum and the locust bean gum is 500:1800:150:90;

[0063] (5) introducing the mixed slurry into a granulator for granulation, the granulated material enters a dryer for drying, the dried material is screened through a vibrating screen, to obtain qualified particles with a particle size of 4mm, introducing the qualified particles into a cooler for cooling, to obtain the compound fertilizer; the water content of the dried material is less than 1.5%.

[0064] The preparation of the coating agent comprises the following steps:

[0065] S1. Mix triazine gum and deionized water, stir for 25 minutes, filter, and take the liquid phase to obtain material E; the ratio of triazine gum to deionized water is 1.5g:150mL.

[0066] S2. Mix zein and ethanol aqueous solution, stir for 35 min to obtain material F; the ratio of zein to ethanol aqueous solution is 3.5 g: 110 mL; the volume fraction of ethanol in the ethanol aqueous solution is 85%;

[0067] S3. Mix materials E and F, add calcium polyphosphate, stir for 7 hours to obtain mixture G, transfer mixture G to a molding mold and let stand for 16 hours, freeze at -18℃ for 22 hours, and dry under 170Pa vacuum for 2.5 hours to obtain the coating agent; the ratio of materials E, F and calcium polyphosphate is 15mL:9mL:3.5g.

[0068] Example 3

[0069] The preparation of the compound fertilizer includes the following steps:

[0070] (1) Sulfur and anhydrous ethanol are added to a material tank and mixed. The mixture is stirred for 6 hours and heated to 60°C and oscillated for 1 hour to obtain material A. The ratio of sulfur to anhydrous ethanol is 500g:3L.

[0071] (2) Let the material A stand until it is clear, take the clear liquid and put it in the processing tank, add distilled water and mix, shake for 2 hours, add sodium dodecyl sulfate and shake for 2 hours, add coating agent to the processing tank and shake for 40 minutes to obtain material B, and let it stand for later use.

[0072] The ratio of the clarified liquid, distilled water, sodium dodecyl sulfate, and coating agent is 1L:3L:8g:200g;

[0073] (3) Phosphoric acid is placed in a reaction vessel and heated to 60°C. Ammonia gas is introduced under constant temperature to adjust the pH to 4.8 to obtain slurry C. Slurry C is then passed into a filter press for filtration. The filtrate is collected and placed in a mixing vessel to obtain liquid D.

[0074] The pressure filtration refers to holding the pressure at 50MPa for 20 minutes.

[0075] (4) Take material B and filter it to collect the filter residue. Then, put the filter residue into the mixing tank and mix it with the liquid D. Add guar gum and locust bean gum to the mixing tank and shake for 40 minutes to obtain a mixed slurry.

[0076] The mass ratio of the filter residue, liquid D, guar gum, and locust bean gum is 500:2200:200:100;

[0077] (5) the mixed slurry is introduced into a granulator for granulation, the granulated material is introduced into a dryer for drying, the dried material is introduced into a vibrating screen for screening, qualified particles with a particle size of 5 mm are obtained, the qualified particles are introduced into a cooler for cooling, and the composite fertilizer is obtained.

[0078] The preparation of the coating agent comprises the following steps:

[0079] S1, mix tri-sodium citrate and deionized water, stir for 30 min, filter, and obtain material E from the liquid phase; the dosing ratio of tri-sodium citrate and deionized water is 2 g:200 mL;

[0080] S2, mix zein and an ethanol aqueous solution, stir for 40 min, and obtain material F; the dosing ratio of zein and the ethanol aqueous solution is 4 g:120 mL; the volume fraction of ethanol in the ethanol aqueous solution is 85%;

[0081] S3, mix the material E and the material F, add calcium polyphosphate, stir for 8 h, obtain a mixed liquid G, transfer the mixed liquid G to a forming mold, stand for 18 h, freeze at-20℃ for 24 h, and dry under a vacuum condition of 180 Pa for 3 h, and the coating agent is obtained; the dosing ratio of the material E, the material F and calcium polyphosphate is 20 mL:10 mL:4 g.

[0082] Comparative Example 1

[0083] The difference from Example 1 is that no coating agent is added in step (2), so as to obtain material B without the coating agent.

[0084] Comparative Examples 2-3

[0085] The difference from Example 1 is that the dosing ratio of guar gum and locust bean gum is different in step (4), and the dosing ratio is shown in Table 1.

[0086] Table 1

[0087] Guar gum (mass parts) Locust bean gum (mass parts) Comparative Example 2 180 0 Comparative Example 3 0 180

[0088] Comparative Example 4

[0089] The difference from Example 1 is that no sodium dodecyl sulfate is added in step (2).

[0090] Comparative Example 5

[0091] The difference from Example 1 is that soluble starch is used to replace tri-sodium citrate to prepare material E in step S1 in the preparation process of the coating agent.

[0092] Performance test

[0093] Test Example 1

[0094] The average compressive strength was determined according to the standard GB / T 10212-1988;

[0095] The composite fertilizers prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to the average compressive strength determination according to the above standard, and the test results are shown in Table 2.

[0096] Table 2

[0097] Average compressive strength (MPa) Example 1 68.32 Example 2 69.14 Example 3 71.08 Comparative Example 1 35.46 Comparative Example 2 43.5 Comparative Example 3 46.1 Comparative Example 4 52.39 Comparative Example 5 27.25

[0098] Result analysis

[0099] As shown in Table 2, the average compressive strength of the composite fertilizer prepared in Comparative Example 1 was greatly reduced due to the absence of the coating agent; the average compressive strength of the composite fertilizer prepared in Comparative Examples 2-3 was greatly reduced due to the different ratios of guar gum and locust bean gum; the average compressive strength of the composite fertilizer prepared in Comparative Example 4 was reduced due to the absence of sodium dodecyl sulfate; and the average compressive strength of the composite fertilizer prepared in Comparative Example 5 was significantly reduced due to the use of soluble starch instead of triazin glue in the preparation of the coating agent.

[0100] Test Example 2

[0101] The coating agents prepared in Examples 1-3 and Comparative Example 5 were subjected to performance tests according to the following method, and the test results are shown in Table 3.

[0102] 1) The prepared coating agent was cut into a cylindrical sample with a radius (r) of 5 cm and a height (h) of 5 cm, dried, and weighed by an electronic balance to obtain the mass of the sample in air m1, then immersed in distilled water to saturate, and the distilled water was fully filled into the pores of the sample by using a heating drum, after soaking for 3 h, the sample was taken out, the distilled water on the surface of the sample was gently wiped off, and the mass of the sample in air at this time m2 was weighed by an electronic balance, and the porosity (θ) of the coating agent was calculated by the following formula.

[0103]

[0104] Note: p 蒸馏水 represents the density of distilled water at room temperature and normal pressure.

[0105] 2) The prepared coating agent was cut into a cylindrical sample with a radius (r) of 5 cm and a height (h) of 5 cm, dried, and weighed by an electronic balance to obtain the mass of the sample in air M1, then the sample was washed with distilled water for 48 h, the distilled water on the surface of the sample was gently wiped off, and the mass of the sample in air at this time M2 was weighed by an electronic balance, and the degradation rate (G) of the coating agent was calculated by the following formula.

[0106]

[0107] Table 3

[0108] Porosity (%) Degradation rate (%) Example 1 83 73 Example 2 84 75 Example 3 81 74 Comparative Example 5 54 59

[0109] Result analysis

[0110] As shown in Table 3, the coating agents prepared in Examples 1-3 have good degradation performance and high porosity; the porosity and degradation rate of the coating agent prepared in Comparative Example 5 are both poorer than those of the coating agent prepared in Example 1.

[0111] Test Example 3

[0112] Test design:

[0113] 1) Test site and time: The test time is from January 2022 to December 2022, and the test site is set in Liuzhuang Village, Quanyang Town, Jieshou City, Anhui Province, with an average annual temperature of 12-21°C, an average annual precipitation of about 978 mm, and an average annual sunshine duration of 2075 hours.

[0114] 2) Test crop: Rape seedlings (purchased from Shouguang Baicaoyuan Seed Industry).

[0115] 3) Test fertilizer: In this test, the composite fertilizers prepared in Examples 1-3 and Comparative Examples 1-5 are applied in the test group, and the Stanley potassium sulfate type composite fertilizer (purchased from Zhejiang Hangzhou Sijifeng Agricultural Store) is applied in the control group.

[0116] 4) Test scheme: 20 mu of land (each mu is 33.33m*20m) are randomly selected, 360 ridges of high ridges are plowed and hoed (each ridge is 20m*0.6m), each ridge is spaced 0.4m, 100 rape seedlings are uniformly planted in each ridge, every 40 ridges is a group, and 9 groups are randomly divided, one group is applied with the Stanley potassium sulfate type composite fertilizer as the control group, and the remaining 8 groups are applied with the composite fertilizers prepared in Examples 1-3 and Comparative Examples 1-5 as the test group.

[0117] 5) Test treatment: The above-mentioned test fertilizers are applied at the seedling stage of rape seedlings, 20-30 kg of fertilizer per mu is applied to the soil at the root of the rape seedlings.

[0118] The test results are shown in Table 4.

[0119] Test Example 4

[0120] Test design:

[0121] 1) Test site and time: The test time is from January 2022 to December 2022, and the test site is set in Liuzhuang Village, Quanyang Town, Jieshou City, Anhui Province, with an average annual temperature of 12-21°C, an average annual precipitation of about 978 mm, and an average annual sunshine duration of 2075 hours.

[0122] 2) Test crop: large spotless fragrant oil wheat (purchased from Hejian City Fuyichun Seed Sales Co., Ltd.).

[0123] 3) Test fertilizer: In this test, the test group applied the compound fertilizer prepared in Examples 1-3 and Comparative Examples 1-5, and the control group applied the Stanley potassium sulfate type compound fertilizer (purchased from Zhejiang Hangzhou Four Seasons Farming Store).

[0124] 4) Test scheme: 20 mu of land (each mu is 33.33 m*20 m) were randomly selected, 360 ridge furrows (each ridge is 20 m*0.6 m) were plowed and hoed out, each ridge was spaced 0.4 m, 100 plants of large spotless fragrant oil wheat were uniformly planted in each ridge, every 40 ridges was a group, and 9 groups were randomly divided, one group applied the Stanley potassium sulfate type compound fertilizer as a control group, and the remaining 8 groups applied the compound fertilizer prepared in Examples 1-3 and Comparative Examples 1-5 as test groups.

[0125] 5) Test treatment: The above-mentioned test fertilizers were applied during the growth period of the large spotless fragrant oil wheat, 20-30 kg of fertilizer per mu was applied to the soil around the roots of the large spotless fragrant oil wheat.

[0126] The test results are shown in Table 4.

[0127] Table 4

[0128]

[0129] Result analysis

[0130] As can be seen from Table 4, the compound fertilizer prepared in Comparative Examples 1-5 has poorer fertilizer efficiency than the compound fertilizer prepared in Example 1 when applied to leafy vegetable plants, resulting in a decrease in the yield of leafy vegetable plants;

[0131] Among them, the sulfur yellow in Comparative Examples 1-3 and Comparative Example 5 has poor combination degree with the phosphorus ammonium slurry, causing sulfur yellow to leak during the drying process and reducing the fertilizer efficiency;

[0132] In Comparative Example 4, the sulfur yellow is not evenly dispersed, resulting in a decrease in the fertilizer efficiency of the prepared compound fertilizer.

[0133] Note: The tri-sodium citrate involved in the present application is from Nanjing Songguan Biotechnology Co., Ltd.; Guar gum is from Hebei Chuangzhengyuan Biotechnology Co., Ltd.; Locust bean gum is from Nanjing Songguan Biotechnology Co., Ltd.; Sulfur is from Taicang City Chuangjian Chemical Co., Ltd.; Phosphoric acid is from Nanjing Chemical Reagent Co., Ltd.; Soluble starch is from Hubei Xinkai Biotechnology Co., Ltd.

[0134] The above merely describes the preferred embodiments of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed with the preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, as long as the changes or modifications do not deviate from the technical solution of the present application. Any modification, change, equivalent change and modification of the above embodiments made according to the technical essence of the present application still belong to the scope of the technical solution of the present application.

Claims

1. A method for preparing a special-purpose sulfur-based compound fertilizer for leafy vegetables, characterized by, The preparation of the compound fertilizer comprises the following steps: (1) mixing sulfur and anhydrous ethanol, stirring, constant temperature oscillation to obtain material A; (2) placing the material A to a clear state, mixing the supernatant with distilled water, oscillation, adding sodium dodecyl sulfate, oscillation, adding a coating agent, oscillation to obtain material B, and standing for standby use; (3) adjusting the pH of phosphoric acid to 4.3-4.8 by passing ammonia gas to obtain slurry C, pressure filtration, and collecting the filtrate to obtain liquid D; (4) filtering material B, collecting the filter residue, then mixing the filter residue with the liquid D, adding guar gum and locust bean gum, and oscillation to obtain a mixed slurry; (5) granulating the mixed slurry, drying, screening, and cooling to obtain the compound fertilizer; The preparation of the coating agent comprises the following steps: S1, mixing tri-sodium citrate and deionized water, stirring, filtering, and obtaining material E from the liquid phase; the amount ratio of the tri-sodium citrate to the deionized water is 1-2 g: 100-200 mL; S2, mixing zein and an ethanol aqueous solution, stirring to obtain material F; the amount ratio of the zein to the ethanol aqueous solution is 3-4 g: 100-120 mL; S3, mixing the material E and the material F, adding calcium polyphosphate, stirring to obtain a mixed liquid G, transferring the mixed liquid G into a forming mold, standing, freezing, and vacuum drying to obtain the coating agent; the amount ratio of the material E, the material F, and the calcium polyphosphate is 10-20 mL: 8-10 mL: 3-4 g.

2. A method of preparing a speciality sulphur-based compound fertilizer for leafy vegetables according to claim 1, characterized in that, The coating agent is a porous degradable material.

3. The method of claim 1, wherein the method is characterized by, In step (1), the amount ratio of the sulfur to the anhydrous ethanol is 500 g: 2-3 L.

4. The method of claim 1, wherein the method is characterized by, In step (2), the amount ratio of the supernatant, the distilled water, the sodium dodecyl sulfate, and the coating agent is 1 L: 2-3 L: 5-8 g: 100-200 g.

5. The method of claim 1, wherein the method is characterized by the steps of: In step (4), the mass ratio of the filter residue, the liquid D, the guar gum, and the locust bean gum is 500: 1200-2200: 100-200: 80-100.

6. The method of claim 1, wherein the method is characterized by, In step (5), the particle size of the compound fertilizer is 3-5 mm.

7. The method of claim 1, wherein the method is characterized by the steps of: In step (5), the water content of the compound fertilizer is less than 1.5%.

8. A compound fertilizer prepared by the preparation method of any one of claims 1-7.

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