Mineral fertilizer composed of medium-low-grade phosphorite and potassium feldspar and preparation method of mineral fertilizer

Abstract

The invention relates to the technical field of mineral fertilizers, in particular to a mineral fertilizer composed of medium and low-grade phosphorite and potassium feldspar and a preparation method of the mineral fertilizer, and the mineral fertilizer comprises macroelements of nitrogen, phosphorus and potassium, medium elements of calcium, magnesium and sulfur, microelements of iron, manganese, zinc, boron, copper and molybdenum, and beneficial elements of silicon and titanium. And meanwhile, the catalyst also contains a silica and alumina tetrahedral frame-shaped structure. Wherein N + P2O5 + K2O is greater than or equal to 9.0%, Ca + Mg + S is greater than or equal to 10.0%, Fe + Mn + Zn + Cu + B + Mo is greater than or equal to 1.0%, Si is greater than or equal to 10.0%, Ti is greater than or equal to 0.02%, and the total content of silica and alumina tetrahedral frame-like substances is greater than or equal to 10%. The mineral fertilizer composed of the medium-and-low-grade phosphorite and the potassium feldspar is a full-nutritional fertilizer, can reduce the application amount of a traditional compound fertilizer when being applied as a base fertilizer, and has the effects of increasing the crop yield, improving the crop quality, loosening soil and the like, and the preparation method is low in raw material cost and low in process energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of mineral fertilizers, and particularly relates to a mineral fertilizer composed of medium and low-grade phosphate rock and potassium feldspar and a preparation method thereof. Background Art

[0002] Mineral fertilizers refer to fertilizers containing certain nutrient elements extracted from mineral resources, which supply nutrients to plants and have the advantages of stable nutrient components, long-lasting effects, low volatility, and low loss. They are important fertilizers indispensable in modern agricultural production. Currently, there are not many research reports on mineral fertilizers, and the raw materials used include coal gangue, dolomite, bentonite, zeolite, magnesite, diatomite, granite, iron ore, medical stone, attapulgite, palygorskite, lime, serpentine, phosphorite, potassium-rich silicate rock, potassium rock, potassium-rich slate, etc. There are relatively few research reports on preparing mineral fertilizers with potassium feldspar or medium and low-grade phosphate rock as the main raw materials, and even fewer research reports on coupling potassium feldspar with medium and low-grade phosphate rock to prepare mineral fertilizers.

[0003] The existing research on potassium extraction from potassium feldspar mainly includes high-energy-consuming high-temperature roasting for potassium extraction above 800 °C, pressure steaming for potassium extraction for more than 8 hours, extremely slow microbial potassium extraction, highly corrosive hydrofluoric acid potassium extraction, and difficult-to-scale closed-system heating and pressurized alkali leaching for potassium extraction. The above technologies are all difficult to achieve industrial production; the existing phosphate rock processing technologies are limited to high-grade phosphate rock (P2O5 content ≥ 28%), and phosphate rock with a P2O5 content of 25% or more can be mixed with high-grade phosphate rock to obtain phosphate rock raw materials with a P2O5 content of 28% for processing and utilization, while phosphate rock with a P2O5 content below 25% (medium and low-grade phosphate rock) has not been effectively utilized at present.

[0004] Developing low-concentration phosphate fertilizers containing medium and trace elements by using medium and low-grade phosphate rock rich in medium and trace elements helps to compensate for or alleviate the lack of medium and trace elements in the soil, which is of great significance for the rational utilization of national phosphate rock resources.

[0005] In view of the above defects, the creator of the present invention finally obtained the present invention through long-term research and practice. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of high energy consumption, strong corrosion, low speed, difficult scaling in potassium extraction from potassium feldspar and the ineffective utilization of medium and low-grade phosphate rock, and provides a mineral fertilizer composed of medium and low-grade phosphate rock and potassium feldspar and a preparation method thereof.

[0007] To achieve the above object, the present invention discloses a mineral fertilizer composed of medium and low-grade phosphate rock and potassium feldspar, characterized in that it includes macronutrients nitrogen, phosphorus and potassium, secondary nutrients calcium, magnesium and sulfur, micronutrients iron, manganese, zinc, boron, copper and molybdenum, beneficial elements silicon and titanium; at the same time, it also includes a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons. The contents of the macronutrients nitrogen, phosphorus and potassium meet the conditions: N + P2O5 + K2O ≥ 9.0%, where N ≥ 1.5%, P2O5 ≥ 5.0%, K2O ≥ 1.5%; the contents of the secondary nutrients calcium, magnesium and sulfur meet the conditions: Ca + Mg + S ≥ 10.0%, where Ca ≥ 5.0%, S ≥ 4.0%, Mg ≥ 0.5%; the contents of the micronutrients iron, manganese, zinc, boron, copper and molybdenum meet the conditions: Fe + Mn + Zn + Cu + B + Mo ≥ 1.0%, where Fe ≥ 0.5%, B ≥ 0.20%, Mn ≥ 0.10%, Zn ≥ 0.10%, Mo ≥ 0.05%, Cu ≥ 0.01%; the contents of the beneficial elements silicon and titanium meet the conditions: Si ≥ 10.0%, where the proportion of water-soluble silicon is not less than 10.0%, Ti ≥ 0.02%; the silicon-oxygen and aluminum-oxygen tetrahedron framework substances are any one or a combination of potassium feldspar, calcium feldspar, magnesium feldspar, and sodium feldspar, and their total content ≥ 10%.

[0008] The present invention also discloses a preparation method of the above-mentioned mineral fertilizer composed of medium and low-grade phosphate rock and potassium feldspar, including the following steps:

[0009] Including the following steps:

[0010] S1, Mix the phosphate rock powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate and water evenly to obtain a wet material, and control the water content ≤ 20%;

[0011] S2, Continuously inject the obtained wet material into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the material;

[0012] S3, Continuously pump concentrated sulfuric acid into the vertical reactor to quickly react with the phosphate rock in the wet material;

[0013] S4, The material in the vertical reactor then enters a horizontal reactor to continue the decomposition of phosphate rock and the extraction of potassium from potassium feldspar. The horizontal reactor uses a screw propeller type rotary stirring, and exhaust is carried out after the reaction ends;

[0014] S5, After the reaction product after exhaust is cooled to 80 - 100 °C, it enters a neutralization reactor, and ammonia is used to neutralize and adjust the pH value of the product to 3 - 9 to obtain a neutralized product;

[0015] S6, After the neutralized product is cooled to room temperature, a mineral fertilizer is obtained, and its free water content ≤ 5.0%.

[0016] In the step S1, the mass parts of phosphorite powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate, and water are as follows: 100 parts of phosphorite powder, 50 - 100 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 parts of ammonium molybdate, 5 parts of ammonium sulfate, and 30 - 35 parts of water.

[0017] In the step S1, the phosphorite powder passes through a 100 - mesh standard sieve, and the potassium feldspar powder passes through a 200 - mesh standard sieve.

[0018] In the step S3, the mass parts of the pumped concentrated sulfuric acid are 35 - 65 parts.

[0019] In the step S3, the amount of the pumped concentrated sulfuric acid meets the following condition: the amount of calcium in the phosphorite is equal to the sum of the amount of P2O5 in the phosphorite and the amount of the added concentrated sulfuric acid, and the concentrated sulfuric acid is 98% H2SO4.

[0020] In the step S3, the reaction time is 5 - 10 min.

[0021] In the step S4, the reaction temperature is 150 - 200 °C, the reaction time is 30 - 60 min, and before entering the step S5, the gas is discharged until the water content in the system ≤ 10%.

[0022] In the step S5, when the mineral fertilizer is applied to alkaline soil, the pH value of the product is adjusted to 3 - 6.

[0023] In the step S5, when the mineral fertilizer is applied to acidic soil, the pH value of the product is adjusted to 7 - 9.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention innovatively constructs a wet - solid reaction system of potassium feldspar, medium - low - grade phosphorite, and sulfuric acid; creates a series process of vertical stirring ball - milling reaction and horizontal screw - propelling reaction; conducts a large number of experimental studies, and obtains a mineral fertilizer with N + P2O5 + K2O ≥ 9.0%, Ca + Mg + S ≥ 10.0%, Fe + Mn + Zn + Cu + B + Mo ≥ 1.0%, Si ≥ 10.0%, Ti ≥ 0.02%, and the total content of feldspar - like substances ≥ 10%.

[0026] 2. The present invention realizes the rapid extraction of potassium from potassium feldspar at medium - low temperature and the efficient utilization of medium - low - grade (P2O5 content < 25%) phosphorite.

[0027] 3. The mineral fertilizer product prepared by the present invention contains silicon - oxygen and aluminum - oxygen tetrahedron framework substances.

[0028] 4. The mineral fertilizer prepared by the present invention has the effects of increasing the yield of crops, improving the quality of crops, and loosening the soil.

[0029] 5. The technology of the present invention can achieve industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the framework structure of feldspar tetrahedron;

[0031] Figure 2 It is the influence of sulfuric acid dosage on the extraction rates of phosphorus and potassium in Example 10;

[0032] Figure 3 It is the influence of sulfuric acid dosage on the extraction rates of phosphorus and potassium in Example 11;

[0033] Figure 4 It is the influence of sulfuric acid dosage on the extraction rates of phosphorus and potassium in Example 12;

[0034] Figure 5 It is the influence of ammonium sulfate dosage on the extraction rates of phosphorus and potassium in Example 13;

[0035] Figure 6 It is the influence of borax dosage on the extraction rates of phosphorus and potassium in Example 14. DETAILED DESCRIPTION OF THE INVENTION

[0036] The following further describes in detail the above and other technical features and advantages of the present invention with reference to the drawings.

[0037] The present invention has carried out experimental research on various medium - and low - grade phosphate rocks and potassium feldspars. The main components of the phosphate rocks and potassium feldspars involved in Examples 1 - 8 are as follows:

[0038] Phosphate rock content (m%): P2O5 15.62, Ca 19.76; Potassium feldspar content (m%): K2O 9.69.

[0039] Explanation of the framework structure of feldspar: Figure 1 It is a schematic diagram of the framework structure of feldspar silicon - oxygen and aluminum - oxygen tetrahedron, which is a network structure composed of [SiO4] and [AlO4] as the framework; the black dots in the middle represent K + , Ca 2+ , Mg 2+ , Na + , which are respectively called potassium feldspar, anorthite, magnesian feldspar, and albite. Under certain conditions, the cations in the network can be exchanged with each other, and potassium ions are more easily replaced by calcium ions, magnesium ions, and sodium ions with smaller radii. When monovalent ions are replaced by divalent ions, the network space of feldspar increases. The network structure has the function of loosening the soil.

[0040] Example 1

[0041] (1) Mix 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 part of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water evenly to obtain wet material;

[0042] (2) Continuously inject the above wet material into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the material;

[0043] (3) Continuously pump 35 parts of concentrated sulfuric acid into the vertical reactor, and react for 10 minutes;

[0044] (4) The material in the vertical reactor enters the horizontal reactor. The horizontal reactor uses a screw propulsion type rotary stirring, the temperature is 150 °C, the reaction time is 60 minutes, and a certain amount of gas is discharged after the reaction. At this time, the water content in the system is 9.38%.

[0045] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used for neutralization to adjust the pH value of the product to 4;

[0046] (6) The obtained mineral fertilizer has a free water content of 4.42%, and its effective component contents are N 1.92%, P2O5 6.15%, K2O 1.58%, Ca 7.42%, S 5.10%, Mg 1.15%, Fe 0.69%, B 0.23%, Mn 0.14%, Zn 0.13%, Cu 0.02%, Mo 0.07%, total Si 12.01%, water-soluble Si 1.43%, Ti 0.08%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 12.32%.

[0047] Example 2

[0048] (1) Mix 100 parts of phosphate rock powder, 100 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 part of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water evenly to obtain wet material;

[0049] (2) Continuously inject the above wet material into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the material;

[0050] (3) Continuously pump 35 parts of concentrated sulfuric acid into the vertical reactor, and react for 10 minutes;

[0051] (4) The material in the vertical reactor enters the horizontal reactor. The horizontal reactor uses a screw propulsion type rotary stirring, the temperature is 150 °C, the reaction time is 60 minutes, and a small amount of gas is discharged after the reaction. At this time, the water content in the system is 8.15%.

[0052] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used for neutralization to adjust the pH value of the product to 3;

[0053] (6) The free water content of the obtained mineral fertilizer is 3.23%, and its effective ingredient content is N 1.58%, P2O5 4.81%, K2O 1.38%, Ca 6.11%, S 3.97%, Mg 0.76%, Fe 0.39%, B 0.20%, Mn 0.09%, Zn 0.10%, Cu 0.01%, Mo 0.05%, total Si 15.00%, water-soluble Si 1.04%, Ti 0.05%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 20.26%.

[0054] Compared with Comparative Example 1, the amount of potassium feldspar powder was increased in this example, and the extraction rates of phosphorus, potassium, calcium, magnesium, iron, etc. all decreased, and the effective nutrient contents of most elements did not reach the set indexes. The main reason is that increasing the amount of potassium feldspar powder leads to a decrease in the water and acid contents in the system, an increase in the system resistance, a decrease in the amount of ionic substances in the system, a decrease in the efficiency of sulfuric acid decomposing phosphate rock, and a decrease in the potassium ion exchange rate in potassium feldspar.

[0055] Example 3

[0056] (1) Mix 100 parts of phosphate rock powder, 100 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 parts of ammonium molybdate, 5 parts of ammonium sulfate, and 35 parts of water evenly to obtain a wet material;

[0057] (2) Continuously inject the above wet material into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the material;

[0058] (3) Continuously pump 45 parts of concentrated sulfuric acid into the vertical reactor and react for 10 min;

[0059] (4) The material in the vertical reactor enters the horizontal reactor, and the horizontal reactor uses a screw propeller to rotate and stir. The temperature is 150 °C, and the reaction time is 60 min. After the reaction, a small amount of gas is discharged. At this time, the water content in the system is 9.45%.

[0060] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used to neutralize and adjust the pH value of the product to 8;

[0061] (6) The free water content of the obtained mineral fertilizer is 4.21%, and its effective ingredient content is N 2.64%, P2O5 5.11%, K2O 2.01%, Ca 6.06%, S 4.95%, Mg 0.90%, Fe 0.55%, B 0.20%, Mn 0.10%, Zn 0.10%, Cu 0.01%, Mo 0.05%, total Si 14.12%, water-soluble Si 1.51%, Ti 0.06%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 19.11%.

[0062] Compared with Example 1, the amounts of potassium feldspar powder, water, and concentrated sulfuric acid were increased in this example. The extraction rates of phosphorus, calcium, etc. increased in this example, while the extraction rate of potassium decreased. This is mainly because the amounts of water and sulfuric acid increased, resulting in an increased decomposition rate of phosphate rock. However, due to the substantial increase in the amount of potassium feldspar used, the total amount of ions that could potentially exchange with potassium decreased relatively, leading to a decrease in the extraction rate of potassium. Compared with Example 2, the changes in the extraction rates of phosphorus, calcium, etc. and the reasons are the same as above. The extraction rate of potassium increased in this example. In addition to the increased water usage reducing the stirring resistance and making the contact between the system materials more sufficient and beneficial to the reaction, it is also because the amount of sulfuric acid increased, the extraction rates of calcium and other ions increased, and the exchange ability with potassium in potassium feldspar increased.

[0063] Example 4

[0064] (1) Mix 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 parts of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water evenly to obtain wet materials;

[0065] (2) Continuously inject the above wet materials into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the materials;

[0066] (3) Continuously pump 40 parts of concentrated sulfuric acid into the vertical reactor, and the reaction lasts for 10 min;

[0067] (4) The materials in the vertical reactor enter the horizontal reactor. The horizontal reactor uses a screw propulsion type for rotary stirring, the temperature is 150 °C, the reaction time is 60 min, and a certain amount of gas is discharged after the reaction. At this time, the water content in the system is 9.47%.

[0068] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used for neutralization to adjust the pH value of the product to 4;

[0069] (6) The obtained mineral fertilizer has a free water content of 4.53%, and its effective component contents are N 1.61%, P2O5 6.72%, K2O 1.67%, Ca 7.32%, S 5.89%, Mg 1.18%, Fe 0.70%, B 0.23%, Mn 0.15%, Zn 0.12%, Cu 0.02%, Mo 0.06%, total Si 11.51%, water-soluble Si 1.51%, Ti 0.09%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 11.61%.

[0070] Compared with Example 1, the amount of concentrated sulfuric acid was increased in this example. The total amount and concentration of sulfuric acid in the system increased, the decomposition rate of phosphate rock was improved, the concentration of calcium and other ions in the system increased, and the exchange ability with potassium ions in potassium feldspar was enhanced, thereby increasing the extraction rate of potassium.

[0071] Example 5

[0072] (1) Mix 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 parts of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water evenly to obtain wet materials;

[0073] (2) Continuously inject the above wet materials into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the materials;

[0074] (3) Continuously pump 45 parts of concentrated sulfuric acid into the vertical reactor, and the reaction is carried out for 10 min;

[0075] (4) The materials in the vertical reactor enter the horizontal reactor. The horizontal reactor uses a screw propeller to rotate and stir. The temperature is 150 °C, the reaction time is 60 min, and a certain amount of gas is discharged after the reaction. At this time, the water content in the system is 9.17%.

[0076] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used for neutralization to adjust the pH value of the product to 4;

[0077] (6) The obtained mineral fertilizer has a free water content of 4.67%, and its effective ingredient content is N 1.72%, P2O5 6.90%, K2O 1.41%, Ca 7.48%, S 6.19%, Mg 1.11%, Fe 0.79%, B 0.22%, Mn 0.14%, Zn 0.12%, Cu 0.02%, Mo 0.06%, total Si 11.11%, water-soluble Si 1.53%, Ti 0.08%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 11.01%.

[0078] Comparing Comparative Example 1 and Example 4, the amount of concentrated sulfuric acid used is increased in this example, the total amount and concentration of sulfuric acid in the system are further increased, and the decomposition rate of phosphate rock is also further improved; however, due to the increase of sulfate radicals in the system, one of the decomposition products of phosphate rock, soluble calcium dihydrogen phosphate, gradually transforms into insoluble calcium sulfate, resulting in a decrease in the concentration of calcium and other ions in the system, and the ability to exchange with potassium ions in potassium feldspar also decreases accordingly, resulting in a decrease in the extraction rate of potassium.

[0079] Example 6

[0080] (1) Mix 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 1.2 parts of zinc sulfate, 0.25 parts of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water evenly to obtain wet materials;

[0081] (2) Continuously inject the above wet materials into a vertical reactor, and the reactor uses a stirring paddle to drive a ball mill to strongly stir the materials;

[0082] (3) Continuously pump 40 parts of concentrated sulfuric acid into the vertical reactor, and react for 10 min;

[0083] (4) The materials in the vertical reactor enter the horizontal reactor. The horizontal reactor uses a screw-propelled rotary stirring method, with a temperature of 150 °C and a reaction time of 60 min. After the reaction, a certain amount of gas is discharged. At this time, the water content in the system is 9.30%.

[0084] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used for neutralization to adjust the pH value of the product to 4;

[0085] (6) The obtained mineral fertilizer has a free water content of 4.57%, and its effective component contents are N 1.89%, P2O5 6.79%, K2O 1.54%, Ca 7.39%, S 5.79%, Mg 1.13%, Fe 0.59%, Mn 0.14%, Zn 0.12%, Cu 0.02%, Mo 0.06%, total Si 12.01%, water-soluble Si 1.28%, Ti 0.08%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 12.11%.

[0086] Compared with Example 4, borax was not added in this example, and the mineral fertilizer does not contain boron, which has little effect on the decomposition rate of phosphate rock, but the extraction rate of potassium has decreased. The main reason is that adding borax not only supplements the essential nutrient element boron for plants, but also brings sodium ions with an ionic radius smaller than that of potassium, thereby improving the ability to displace potassium ions in potassium feldspar, that is, improving the extraction rate of potassium.

[0087] Example 7

[0088] (1) Mix 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 part of ammonium molybdate, and 30 parts of water evenly to obtain wet materials;

[0089] (2) Continuously inject the above wet materials into the vertical reactor, and the reactor uses a stirring paddle to drive the ball mill to strongly stir the materials;

[0090] (3) Continuously pump 40 parts of concentrated sulfuric acid into the vertical reactor, and react for 10 min;

[0091] (4) The materials in the vertical reactor enter the horizontal reactor. The horizontal reactor uses a screw-propelled rotary stirring method, with a temperature of 150 °C and a reaction time of 60 min. After the reaction, a certain amount of gas is discharged. At this time, the water content in the system is 9.41%.

[0092] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reactor, and ammonia is used for neutralization to adjust the pH value of the product to 4;

[0093] (6) The free water content of the obtained mineral fertilizer is 4.64%, and its effective component contents are N 1.54%, P2O5 6.80%, K2O 1.57%, Ca 7.32%, S 5.89%, Mg 1.18%, Fe 0.70%, B 0.23%, Mn 0.15%, Zn 0.12%, Cu 0.02%, Mo 0.06%, total Si 11.51%, water-soluble Si 1.51%, Ti 0.09%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 11.61%.

[0094] Comparing with Example 4, ammonium sulfate was not added in this example, which had little effect on the decomposition rate of phosphate rock, but the extraction rate of potassium decreased. The main reason is that adding ammonium sulfate can increase the solubility of calcium sulfate, that is, increase the calcium ion concentration in the system, thereby improving the ability to displace potassium ions from potassium feldspar, that is, improving the extraction rate of potassium.

[0095] Example 8

[0096] (1) Mix 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 part of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water evenly to obtain a wet material;

[0097] (2) Continuously inject the above wet material into a vertical reaction kettle, and the reaction kettle uses a stirring paddle to drive a ball mill to strongly stir the material;

[0098] (3) Continuously pump 40 parts of concentrated sulfuric acid into the vertical reaction kettle, and the reaction lasts for 10 min;

[0099] (4) The material in the vertical reaction kettle enters the horizontal reaction kettle. The horizontal reaction kettle uses a screw propulsion type for rotary stirring, the temperature is 200 °C, the reaction time is 60 min, and a certain amount of gas is discharged after the reaction. At this time, the water content in the system is 8.33%.

[0100] (5) After the reaction product is cooled to 100 °C, it enters the neutralization reaction kettle, and ammonia is used for neutralization to adjust the pH value of the product to 4;

[0101] (6) The free water content of the obtained mineral fertilizer is 3.93%, and its effective component contents are N 1.92%, P2O5 6.77%, K2O 1.90%, Ca 7.38%, S 5.79%, Mg 1.17%, Fe 0.71%, B 0.22%, Mn 0.13%, Zn 0.12%, Cu 0.02%, Mo 0.06%, total Si 12.11%, water-soluble Si 1.60%, Ti 0.08%, and the content of feldspar substances with a framework structure of silicon-oxygen and aluminum-oxygen tetrahedrons is 10.99%.

[0102] Compared with Comparative Example 4, the temperature in the horizontal reactor was increased in this example. The extraction rates of phosphorus, calcium, etc. changed little, but the extraction rate of potassium increased significantly. This is mainly because the increase in temperature enhanced the ionic energy in the system, improving the ability to exchange with potassium ions in potassium feldspar, thereby increasing the extraction rate of potassium. When the temperature exceeds 200 °C, the system pressure will exceed 1.6 MPa, which belongs to the medium-pressure range, and the requirements for industrial engineering design will increase. In addition, the reaction heat energy of the present invention can naturally heat the system materials to 150 °C and above. Therefore, the temperature range of the present invention is set at 150 °C - 200 °C.

[0103] Example 9

[0104] A fertilizer efficiency test was carried out on pakchoi. Fertilizer was spread per mu, and then rotary tillage was carried out for land preparation. Two treatments were set, and other field management was kept consistent. Treatment 1: 30 kg of N-P2O5-K2O = 15-15-15 compound fertilizer was spread per mu; Treatment 2: 30 kg of the mineral fertilizer after cooling in Example 4 was spread per mu. The relevant detection results during the harvest of pakchoi are as follows:

[0105] (1) Chlorophyll balance value of pakchoi leaves (detected before harvest at around 10 am): The average chlorophyll value of Treatment 1 was 46.56 (SPAD), and the average chlorophyll value of Treatment 2 was 49.6 (SPAD);

[0106] (2) Average weight of leaves with an equal diameter (80 mm) area: The average weight of Treatment 1 was 20.2 g, and the average weight of Treatment 2 was 22 g;

[0107] (3) Yield per mu: The yield per mu of Treatment 1 was 2600 kg, and the yield per mu of Treatment 2 was 2790 kg;

[0108] (4) Powdery mildew situation: Treatment 1 had obvious powdery mildew symptoms; Treatment 2 had no powdery mildew symptoms;

[0109] (5) Soil porosity: The soil porosity before fertilization was 32%. After the harvest of pakchoi, the soil porosity of Treatment 1 was 33%, and the soil porosity of Treatment 2 was 46%.

[0110] Compared with the N-P2O5-K2O = 15-15-15 compound fertilizer, the mineral fertilizer obtained in Example 4 has good effects of increasing production, improving quality, and loosening the soil. This is mainly because the mineral fertilizer obtained in Example 4 not only contains a large amount of various mineral elements, but also contains potassium feldspar, albite, anorthite, and magnesium feldspar with a framework structure of silicon oxygen and aluminum oxygen tetrahedra, which can promote soil loosening.

[0111] Example 10

[0112] This example follows the operation process of Example 1, with the differences being: the wet materials are 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 part of ammonium molybdate, 5 parts of ammonium sulfate, and 30 parts of water; the sulfuric acid dosage is changed (30 parts, 35 parts, 40 parts, 45 parts, and 50 parts respectively), and 5 groups of mineral fertilizers are prepared. The experimental results are shown in Figure 2 , and the optimal concentrated sulfuric acid dosage is about 38 kg; the main component contents of the phosphate rock powder and potassium feldspar powder in this experiment are shown in Table 1.

[0113] Table 1 Main components of phosphate rock powder and potassium feldspar powder in this example

[0114] Mineral powder Project Content / % Project Content / % Phosphate rock powder <![CDATA[P2O5]]> 15.62 Ca 19.76 Potassium feldspar powder <![CDATA[K2O]]> 9.69

[0115] Example 11

[0116] This example follows the operation process of Example 1, with the differences being: the wet materials are 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, and 35 parts of water; the sulfuric acid dosage is changed (40 parts, 45 parts, 50 parts, 55 parts, and 60 parts respectively), and 5 groups of mineral fertilizers are prepared. The experimental results are shown in Figure 3 , and the optimal concentrated sulfuric acid dosage is around 50 kg; the main component contents of the phosphate rock powder and potassium feldspar powder in this experiment are shown in Table 2.

[0117] Table 2 Main components of phosphate rock powder and potassium feldspar powder in this example

[0118] Mineral powder Project Content / % Project Content / % Phosphate rock powder <![CDATA[P2O5]]> 19.28 Ca 26.04 Potassium feldspar powder <![CDATA[K2O]]> 9.69

[0119] Example 12

[0120] This example follows the operation process of Example 1, with the differences being: the wet materials are 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, and 35 parts of water; the sulfuric acid dosage is changed (50 parts, 55 parts, 60 parts, 65 parts, and 70 parts respectively), and 5 groups of mineral fertilizers are prepared. The experimental results are shown in Figure 4 , and the optimal concentrated sulfuric acid dosage is around 59 kg; the main component contents of the phosphate rock powder and potassium feldspar powder in this experiment are shown in Table 3.

[0121] Table 3 Main components of phosphate rock powder and potassium feldspar powder in this example

[0122] Mineral powder Project Content / % Project Content / % Phosphate rock powder <![CDATA[P2O5]]> 24.9 Ca 31.27 Potassium feldspar powder <![CDATA[K2O]]> 9.69

[0123] It can be seen from Figure 2 - Figure 4 that as the sulfuric acid dosage increases, the phosphorus extraction rate gradually increases, and the potassium extraction shows a parabolic shape of first increasing and then decreasing. This is because phosphorus is extracted as the phosphate rock is decomposed by sulfuric acid, while potassium is mainly released when ions with an ionic radius smaller than K + (such as Ca 2+ etc.) in the decomposition products of phosphate rock enter potassium feldspar to displace K +ions. Since the amount of Ca 2+ and other plasma existing in the reaction system determines the extraction rate of potassium. The products of sulfuric acid decomposing phosphate rock are slightly water-soluble calcium sulfate and phosphoric acid. Phosphoric acid can also participate in decomposing phosphate rock to form water-soluble calcium dihydrogen phosphate. When the amount of sulfuric acid is too small, the phosphate rock is not completely decomposed, and the amount of soluble calcium dihydrogen phosphate in the system is small, that is, the amount of calcium ions in the solution is small, and the extraction rate of potassium is low; when the amount of sulfuric acid is too large, although the phosphate rock is decomposed more completely, the excessive sulfuric acid will combine with calcium ions in the solution to form slightly water-soluble calcium sulfate, that is, greatly reducing the number of calcium ions in the solution, resulting in a decrease in the extraction rate of potassium. It can be seen that there is an optimal range for the amount of sulfuric acid. Since the amount of other cation substances in the phosphate rock that react with sulfuric acid and phosphoric acid is much smaller than that of calcium ions, therefore, this optimal range mainly depends on the calcium (Ca) and phosphorus (P2O5) contents in the phosphate rock powder. The optimal range of sulfuric acid consumption should satisfy: the amount of substance of calcium in the phosphate rock is equal to the sum of the amount of substance of P2O5 in the phosphate rock and the amount of substance of concentrated sulfuric acid added. There may be a little deviation between the theoretical calculation and the actual experimental results because a small amount of elements such as magnesium, sodium, and iron in different phosphate rocks also consume sulfuric acid, and the Mg 2+ , Na + ionic radii are all smaller than K + , and they will also participate in the potassium ion exchange in potassium feldspar; in addition, there is also a small amount of fluorine in the phosphate rock, and fluorine can decompose potassium feldspar to release potassium. However, the content of these elements is very small, and the influence on the sulfuric acid consumption is small. Therefore, the deviation caused by the sulfuric acid consumption will not be too large, and the relative error usually does not exceed 5%. The theoretical calculation results of the above experiments are shown in Table 4, which is basically consistent with the Figure 1 - Figure 3 experimental results.

[0124] Table 4 Understanding and calculated values of the optimal sulfuric acid consumption for different phosphate rock powders (100 kg)

[0125]

[0126] Example 13

[0127] This example was operated according to the procedure of Example 4, with the difference being: changing the amount of ammonium sulfate (0 parts, 3 parts, 4 parts, 5 parts, and 6 parts respectively), and 5 groups of mineral fertilizers were prepared.

[0128] It can be seen from Figure 5 that the amount of ammonium sulfate has little effect on the phosphorus extraction rate, but has a certain effect on the potassium extraction rate. With the increase of the amount of ammonium sulfate, the potassium extraction rate increases. For the phosphate rock used in this invention patent, when the addition amount of ammonium sulfate in the 100-part phosphate rock system reaches 5 parts or more, the influence on the extraction rate of potassium in potassium feldspar becomes smaller. The reason why adding ammonium sulfate can increase the extraction rate of potassium is that the presence of ammonium ions can promote the dissolution of calcium sulfate, increase the calcium ion concentration in the system, and thus increase the extraction rate of potassium.

[0129] Example 14

[0130] This example was operated according to the operation process of Example 4, with the difference that the dosages of borax were changed (0 part, 1.2 parts, 2.4 parts, 4.8 parts, and 6.0 parts respectively), and 5 groups of mineral fertilizers were prepared.

[0131] It can be seen from Figure 6 that borax has little effect on the phosphorus extraction rate, but has a certain effect on the potassium extraction rate. With the increase of the borax dosage, the potassium extraction rate increases; in this experimental system, when the borax addition amount reaches 4.8 parts, continuing to increase the borax dosage results in a very small increase in the potassium extraction rate. The reason why adding borax can increase the potassium extraction rate is that borax contains 12% sodium ions, and the sodium ion radius is much smaller than that of potassium ions, which is likely to displace potassium ions in potassium feldspar under certain conditions, thereby increasing the potassium extraction rate.

[0132] The above are only the preferred embodiments of the present invention, which are illustrative rather than restrictive to the present invention. Those skilled in the art understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, but all will fall within the protection scope of the present invention.

Claims

1. A mineral fertilizer composed of medium and low grade phosphate rock and potassium feldspar, characterized in that: It includes macroelements of nitrogen, phosphorus and potassium, medium elements of calcium, magnesium and sulfur, trace elements of iron, manganese, zinc, boron, copper, molybdenum, and beneficial elements of silicon and titanium; it also includes silicon oxygen and aluminum oxygen tetrahedral frame structure, the content of the macroelements of nitrogen, phosphorus and potassium meets the conditions: N+P2O5+K2O≥9.0%, wherein N≥1.5%, P2O5≥5.0%, K2O≥1.5%; the content of the medium elements of calcium, magnesium and sulfur meets the conditions: Ca+Mg+S≥10.0%, wherein Ca≥5.0%, S≥4.0%, Mg≥0.5%; the content of the trace elements of iron, manganese, zinc, boron, copper and molybdenum meets the conditions: The content of the beneficial elements silicon and titanium meets the conditions: Si ≥ 10.0%, of which the proportion of water-soluble silicon is not less than 10.0%, and Ti ≥ 0.02%; the silicon oxygen and aluminum oxygen tetrahedral framework material is any one or a combination of potassium feldspar, calcium feldspar, magnesium feldspar and sodium feldspar, and its total content is ≥ 10%.

2. A method for preparing the mineral fertilizer composed of medium and low grade phosphate rock and potassium feldspar as claimed in claim 1, characterized in that: The following steps are involved: S1, mixing phosphate rock powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate and water evenly to obtain wet material, and controlling the water content to ≤20%; S2, continuously injecting the obtained wet materials into a vertical reactor, and using a stirring paddle to drive a ball mill to vigorously stir the materials in the reactor; S3, continuously pumping concentrated sulfuric acid into the vertical reactor to react rapidly with the phosphate rock in the wet material; S4, the materials in the vertical reactor enter the horizontal reactor to continue the decomposition of phosphate rock and the extraction of potassium from potassium feldspar. The horizontal reactor adopts screw propulsion type rotary stirring, and exhausts after the reaction is completed; S5, the reaction product after exhaust is cooled to 80-100°C and then enters the neutralization reactor, where ammonia is used to neutralize and adjust the pH value of the product to 3-9 to obtain a neutralized product; S6, the neutralized product is cooled to room temperature to obtain a mineral fertilizer, wherein the free water content of the mineral fertilizer is ≤5.0%.

3. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S1, the mass proportions of phosphate rock powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate and water are respectively: 100 parts of phosphate rock powder, 50-100 parts of potassium feldspar powder, 4.8 parts of borax, 1.2 parts of zinc sulfate, 0.25 parts of ammonium molybdate, 5 parts of ammonium sulfate and 30-35 parts of water.

4. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In the step S1, the phosphate rock powder is passed through a 100-mesh standard sieve, and the potassium feldspar powder is passed through a 200-mesh standard sieve.

5. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S3, the mass fraction of concentrated sulfuric acid pumped in is 35-65 parts.

6. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S3, the amount of concentrated sulfuric acid pumped in satisfies the following condition: the amount of calcium in the phosphate rock is equal to the sum of the amount of P2O5 in the phosphate rock and the amount of concentrated sulfuric acid added, and the concentrated sulfuric acid is 98% H2SO4.

7. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S3, the reaction time is 5-10 min.

8. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S4, the reaction temperature is 150-200° C., the reaction time is 30-60 min, and before entering step S5, the gas is discharged until the water content of the system is ≤10%.

9. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S5, when the mineral fertilizer is applied to alkaline soil, the pH value of the product is adjusted to 3-6.

10. The method for preparing a mineral fertilizer composed of medium- and low-grade phosphate rock and potassium feldspar according to claim 2, characterized in that: In step S5, when the mineral fertilizer is applied to acidic soil, the pH value of the product is adjusted to 7-9.

Images