A mineral fertilizer composed of low and medium grade phosphate rock and potassium feldspar and a preparation method thereof

Abstract

The present application relates to the technical field of mineral fertilizer, in particular to a mineral fertilizer composed of medium and low grade phosphate rock and potassium feldspar and a preparation method thereof, the product mineral fertilizer contains macroelements N, P, K, medium elements Ca, Mg, S, microelements Fe, Mn, Zn, B, Cu, Mo, beneficial elements Si and Ti, and also contains silicon-oxygen and aluminum-oxygen tetrahedral framework 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 silicon-oxygen and aluminum-oxygen tetrahedral framework structure is greater than or equal to 10%. The mineral fertilizer composed of medium and low grade phosphate rock and potassium feldspar is a full-nutrient fertilizer, and as base fertilizer, the application amount of traditional compound fertilizer can be reduced, and the mineral fertilizer has the effects of increasing crop yield, improving crop quality, loosening soil and the like, and the preparation method has low raw material cost and low process energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mineral fertilizer, in particular to a mineral fertilizer composed of low-grade phosphate rock and potassium feldspar and a preparation method thereof. BACKGROUND

[0002] Mineral fertilizer refers to a fertilizer containing certain nutrient elements extracted from mineral resources, which provides nutrient substances for plants, has advantages of stable nutrient composition, long-lasting effect, non-volatility and non-leaching, and is an important fertilizer indispensable in modern agricultural production. At present, there are few reports on mineral fertilizer research, and the raw materials used include coal gangue, dolomite, bentonite, zeolite, magnesite, diatomite, granite, iron ore, mica schist, attapulgite, palygorskite, lime, serpentine, phosphate rock, potassium-rich silicate rock, potassium rock and potassium-rich slate. There are relatively few reports on the preparation of mineral fertilizer using potassium feldspar or low-grade phosphate rock as the main raw material, and even fewer reports on the preparation of mineral fertilizer by coupling potassium feldspar and low-grade phosphate rock.

[0003] The existing potassium feldspar potassium extraction research mainly includes high-energy consumption high-temperature roasting above 800 DEG C for potassium extraction, more than 8 hours of pressure steam for potassium extraction, extremely slow microbial potassium extraction, extremely corrosive hydrofluoric acid potassium extraction, and difficult to scale closed system heating and pressure alkali leaching potassium extraction. The above technologies are difficult to realize industrial production; the existing phosphate rock processing technology is limited to high-grade phosphate rock (P2O5 content ≥ 28%), and P2O5 content of 25% and above phosphate rock can be mixed with high-grade phosphate rock to obtain P2O5 content of 28% phosphate rock raw material for processing and utilization, and P2O5 content below 25% phosphate rock (low-grade phosphate rock) is not effectively utilized at present.

[0004] Developing low-concentration phosphate fertilizer containing medium and trace elements by using 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, and has important significance for the rational utilization of state-owned phosphate rock resources.

[0005] In view of the above defects, the present inventors have finally obtained the present application after long-term research and practice. SUMMARY

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

[0007] In order to achieve the above-mentioned purpose, the mineral fertilizer composed of low-grade phosphate ore and potassium feldspar is disclosed, characterized in that it comprises macroelements of nitrogen, phosphorus and potassium, medium elements of calcium, magnesium and sulfur, trace elements of iron, manganese, zinc, boron, copper and molybdenum, beneficial elements of silicon and titanium, and a silicon-oxygen and aluminum-oxygen tetrahedral framework structure; the content of the macroelements of nitrogen, phosphorus and potassium satisfies the condition that N+P2O5+K2O≥9.0%, wherein N≥1.5%, P2O5≥5.0%, and K2O≥1.5%; the content of the medium elements of calcium, magnesium and sulfur satisfies the condition that Ca+Mg+S≥10.0%, wherein Ca≥5.0%, S≥4.0%, and Mg≥0.5%; the content of the trace elements of iron, manganese, zinc, boron, copper and molybdenum satisfies the condition that Fe+Mn+Zn+Cu+B+Mo≥1.0%, wherein Fe≥0.5%, B≥0.20%, Mn≥0.10%, Zn≥0.10%, Mo≥0.05%, and Cu≥0.01%; the content of the beneficial elements of silicon and titanium satisfies the condition that Si≥10.0%, wherein the proportion of water-soluble silicon is not less than 10.0%, and Ti≥0.02%; and the silicon-oxygen and aluminum-oxygen tetrahedral framework structure is any one or a combination of several of potassium feldspar, calcium feldspar, magnesium feldspar and sodium feldspar, and the total content thereof is ≥10%.

[0008] The application further discloses a preparation method of the mineral fertilizer composed of low-grade phosphate ore and potassium feldspar, comprising the following steps:

[0009] comprising the following steps:

[0010] S1, uniformly mixing phosphate ore powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate and water to obtain wet materials, and controlling the water content to be ≤20%;

[0011] S2, continuously injecting the obtained wet materials into a vertical reaction kettle, and using a stirring paddle to drive ball mills to strongly stir the materials;

[0012] S3, continuously pumping concentrated sulfuric acid into the vertical reaction kettle to react with the phosphate ore in the wet materials;

[0013] S4, the materials in the vertical reaction kettle enter a horizontal reaction kettle to continue the decomposition of the phosphate ore and the extraction of potassium from the potassium feldspar, the horizontal reaction kettle adopts screw propulsion type rotary stirring, and exhausts after the reaction is completed;

[0014] S5, after the reaction products are cooled to 80-100°C, the products enter a neutralization reaction kettle to be neutralized by ammonia to adjust the pH value of the products to 3-9, and neutralized products are obtained;

[0015] S6, after the neutralized products are cooled to room temperature, the mineral fertilizer is obtained, and the free water content is ≤5.0%.

[0016] The mass fraction of the phosphorite powder, the potassium feldspar powder, the borax, the zinc sulfate, the ammonium molybdate, the ammonium sulfate and the water in the step S1 is respectively: the phosphorite powder 100 parts, the potassium feldspar powder 50-100 parts, the borax 4.8 parts, the zinc sulfate 1.2 parts, the ammonium molybdate 0.25 parts, the ammonium sulfate 5 parts and the water 30-35 parts.

[0017] The phosphorite powder in the step S1 is passed through a 100-mesh standard sieve, and the potassium feldspar powder is passed through a 200-mesh standard sieve.

[0018] The mass fraction of the concentrated sulfuric acid pumped in the step S3 is 35-65 parts.

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

[0020] The reaction time in the step S3 is 5-10 min.

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

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

[0023] The product pH value is adjusted to 7-9 when the mineral fertilizer is applied to the acid soil in the step S5.

[0024] The beneficial effects of the present application compared with the prior art are:

[0025] 1. The present application innovatively constructs a feldspar, a low-medium grade phosphorite and a sulfuric acid wet solid reaction system; creates a vertical stirring ball milling reaction and a horizontal screw propelling reaction series process; and develops a large amount of experimental research, 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 total content of feldspar substances≥10%;

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

[0027] 3. The mineral fertilizer product prepared by the present application contains silicon-oxygen and aluminum-oxygen tetrahedral frame substances;

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

[0029] 5、The present application can realize industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic diagram of feldspar tetrahedral frame structure;

[0031] Figure 2 is the influence of the amount of sulfuric acid on the extraction rate of potassium phosphate in Example 10;

[0032] Figure 3 is the influence of the amount of sulfuric acid on the extraction rate of potassium phosphate in Example 11;

[0033] Figure 4 is the influence of the amount of sulfuric acid on the extraction rate of potassium phosphate in Example 12;

[0034] Figure 5 is the influence of the amount of ammonium sulfate on the extraction rate of potassium phosphate in Example 13;

[0035] Figure 6 is the influence of the amount of borax on the extraction rate of potassium phosphate in Example 14. DETAILED DESCRIPTION

[0036] The above and other technical features and advantages of the present application will be more apparent from the following description with reference to the attached drawings.

[0037] The present application has carried out a variety of low-grade phosphate rock and potash feldspar experimental research work, and the main components of the phosphate rock and potash feldspar involved in Examples 1-8 are as follows:

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

[0039] Explanation of feldspar frame structure: Figure 1 is a schematic diagram of feldspar silicon-oxygen and aluminum-oxygen tetrahedral frame structure, which is a network structure composed of [SiO4] and [AlO4] as the skeleton; the black dots in the middle represent K + , Ca 2+ , Mg 2+ , Na + , respectively, which are called potassium feldspar, calcium feldspar, magnesium feldspar, and sodium feldspar. 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 loose soil.

[0040] Example 1

[0041] (1) mixed uniformly 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 to obtain a wet material;

[0042] (2) continuously injected the wet material into a vertical reaction kettle, and the vertical reaction kettle was used to perform strong stirring of the material by means of a stirring paddle driving a ball mill;

[0043] (3) continuously pumped 35 parts of concentrated sulfuric acid into the vertical reaction kettle, and the reaction was performed for 10 minutes;

[0044] (4) the material in the vertical reaction kettle was transferred into a horizontal reaction kettle, the horizontal reaction kettle was used to perform rotary stirring by means of a screw propelling, the temperature was 150°C, the reaction time was 60 minutes, a certain amount of gas was discharged after the reaction was completed, and the water content in the system at this time was 9.38%.

[0045] (5) the reaction product was cooled to 100°C and then was transferred into a neutralization reaction kettle, ammonia was used to neutralize and adjust the pH value of the product to 4;

[0046] (6) the free water content of the obtained mineral fertilizer was 4.42%, the effective component content was 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 feldspar-like material content of the silicon-oxygen and aluminum-oxygen tetrahedral framework structure was 12.32%.

[0047] Example 2

[0048] (1) mixed uniformly 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 to obtain a wet material;

[0049] (2) continuously injected the wet material into a vertical reaction kettle, and the vertical reaction kettle was used to perform strong stirring of the material by means of a stirring paddle driving a ball mill;

[0050] (3) continuously pumped 35 parts of concentrated sulfuric acid into the vertical reaction kettle, and the reaction was performed for 10 minutes;

[0051] (4) the material in the vertical reaction kettle was transferred into a horizontal reaction kettle, the horizontal reaction kettle was used to perform rotary stirring by means of a screw propelling, the temperature was 150°C, the reaction time was 60 minutes, a certain amount of gas was discharged after the reaction was completed, and the water content in the system at this time was 9.38%.

[0052] (5) the reaction product was cooled to 100°C and then was transferred into a neutralization reaction kettle, ammonia was used to neutralize and adjust the pH value of the product to 4;

[0053] (6) The free water content of the obtained mineral fertilizer is 3.23%, and the 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 feldspar-like material content of the silicon-oxygen and aluminum-oxygen tetrahedral framework structure is 20.26%.

[0054] Compared with Comparative Example 1, the potassium feldspar powder amount is increased in this example, and the extraction rates of phosphorus, potassium, calcium, magnesium, iron and the like are all reduced, and the effective nutrient content of most elements cannot reach the set index. The main reason is that the increase of the potassium feldspar powder amount leads to the decrease of the water and acid content in the system, the increase of the system resistance, the decrease of the ion state substance amount in the system, the decrease of the efficiency of the sulfuric acid decomposition of the phosphate rock, and the decrease of the potassium ion exchange rate in the potassium feldspar.

[0055] Example 3

[0056] (1) 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 are uniformly mixed to obtain a wet material;

[0057] (2) The wet material is continuously injected into a vertical reaction kettle, and the vertical reaction kettle is used for strong stirring of the material in a mode that a stirring paddle drives a ball mill;

[0058] (3) 45 parts of concentrated sulfuric acid are continuously pumped into the vertical reaction kettle, and reacted for 10 minutes;

[0059] (4) The material in the vertical reaction kettle enters a horizontal reaction kettle, the horizontal reaction kettle is used for rotary stirring in a screw propelling mode, the temperature is 150°C, the reaction time is 60 minutes, and a small amount of gas is discharged after the reaction is completed, 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 a neutralization reaction kettle, and the pH value of the product is adjusted to 8 by ammonia neutralization;

[0061] (6) The free water content of the obtained mineral fertilizer is 4.21%, and the 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 feldspar-like material content of the silicon-oxygen and aluminum-oxygen tetrahedral framework structure is 19.11%.

[0062] Compared with Example 1, the amount of potassium feldspar powder, water and concentrated sulfuric acid is increased, the extraction rate of phosphorus, calcium and other elements is increased, and the extraction rate of potassium is decreased. The main reason is that the amount of water and sulfuric acid is increased, the decomposition rate of phosphate rock is increased, but the amount of potassium feldspar is greatly increased, and the total amount of ions that can exchange with potassium is relatively reduced, resulting in a decrease in the extraction rate of potassium. Compared with Example 2, the change in the extraction rate of phosphorus, calcium and other elements and its reason are the same as above, and the extraction rate of potassium is increased. In addition to the increase in water amount, the stirring resistance is reduced, the material contact in the system is more sufficient, which is beneficial to the reaction, and the extraction rate of potassium is increased because the amount of sulfuric acid is increased, the extraction rate of calcium ions is increased, and the exchange ability of potassium in potassium feldspar is increased.

[0063] Example 4

[0064] (1) 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 are mixed uniformly to obtain a wet material;

[0065] (2) The above wet material is continuously injected into a vertical reaction kettle, and the vertical reaction kettle is used for strong stirring of the material by means of stirring paddle driving ball mill;

[0066] (3) 40 parts of concentrated sulfuric acid are continuously pumped into the vertical reaction kettle, and the reaction is carried out for 10 minutes;

[0067] (4) The material in the vertical reaction kettle enters a horizontal reaction kettle, the horizontal reaction kettle is used for rotary stirring by means of screw propelling, the temperature is 150°C, the reaction time is 60 minutes, a certain amount of gas is discharged after the reaction is completed, and the water content in the system is 9.47% at this time.

[0068] (5) After the reaction product is cooled to 100°C, it enters a neutralization reaction kettle, and the pH value of the product is adjusted to 4 by ammonia neutralization;

[0069] (6) The free water content of the obtained mineral fertilizer is 4.53%, and the effective ingredient content is 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 material with a four-faced structure of silicon-oxygen and aluminum-oxygen tetrahedron is 11.61%.

[0070] Compared with Example 1, the amount of concentrated sulfuric acid is increased, the total amount and concentration of sulfuric acid in the system are increased, the decomposition rate of phosphate rock is increased, the concentration of calcium ions in the system is increased, the exchange ability of potassium ions in potassium feldspar is improved, and the extraction rate of potassium is increased.

[0071] Example 5

[0072] (1) 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 were mixed uniformly to obtain a wet material;

[0073] (2) The wet material was continuously injected into a vertical reaction kettle, and the reaction kettle was used to perform strong stirring of the material by means of a stirring paddle driving a ball mill;

[0074] (3) 45 parts of concentrated sulfuric acid were continuously pumped into the vertical reaction kettle, and the reaction was performed for 10 minutes;

[0075] (4) The material in the vertical reaction kettle was transferred into a horizontal reaction kettle, the horizontal reaction kettle was used to perform rotary stirring by means of a screw propelling, the temperature was 150°C, the reaction time was 60 minutes, a certain amount of gas was discharged after the reaction was completed, and the water content in the system at this time was 9.17%.

[0076] (5) The reaction product was cooled to 100°C and then was transferred into a neutralization reaction kettle, ammonia was used for neutralization to adjust the pH value of the product to 4;

[0077] (6) The free water content of the obtained mineral fertilizer was 4.67%, the effective component content was 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-like material with a four-face structure of silicon-oxygen and aluminum-oxygen tetrahedron was 11.01%.

[0078] Compared with Comparative Example 1 and Example 4, the amount of concentrated sulfuric acid was increased in the present example, the total amount and concentration of sulfuric acid in the system were further increased, and the decomposition rate of phosphate rock was further improved; however, due to the increase of sulfate in the system, one of the decomposition products of phosphate rock, soluble calcium dihydrogen phosphate, gradually converted into insoluble calcium sulfate, thereby causing the concentration of calcium ions in the system to decrease, and the exchange capacity with potassium ions in potassium feldspar also decreased, resulting in a decrease in the extraction rate of potassium.

[0079] Example 6

[0080] (1) 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 were mixed uniformly to obtain a wet material;

[0081] (2) The wet material was continuously injected into a vertical reaction kettle, and the reaction kettle was used to perform strong stirring of the material by means of a stirring paddle driving a ball mill;

[0082] (3) continuously pump concentrated sulfuric acid 40 parts into the vertical reaction kettle, and the reaction is 10 min;

[0083] (4) the material in the vertical reaction kettle enters the horizontal reaction kettle, the horizontal reaction kettle adopts screw propelling type rotary stirring, the temperature is 150°C, the reaction time is 60 min, a certain amount of gas is discharged after the reaction is completed, and the water content in the system at this time is 9.30%.

[0084] (5) after the reaction product is cooled to 100°C, it enters the neutralization reaction kettle, and is neutralized with ammonia to adjust the pH value of the product to 4;

[0085] (6) the free water content of the obtained mineral fertilizer is 4.57%, the effective ingredient content is 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 the feldspar substance with a four-face structure of silicon-oxygen and aluminum-oxygen tetrahedron is 12.11%.

[0086] In the comparative example 4, borax is not added, the mineral fertilizer does not contain boron, and the decomposition rate of the phosphate rock has little effect on the potassium extraction rate, and the main reason is that the addition of borax not only supplements the necessary nutrient element boron for plants, but also brings sodium ions with a smaller ionic radius than potassium, thereby improving the ability to displace potassium ions in potassium feldspar, that is, improving the potassium extraction rate.

[0087] Example 7

[0088] (1) uniformly 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 and 30 parts of water to obtain wet material;

[0089] (2) continuously inject the above wet material into the vertical reaction kettle, and the reaction kettle adopts the mode of ball mill driven by stirring paddle for strong stirring of the material;

[0090] (3) continuously pump concentrated sulfuric acid 40 parts into the vertical reaction kettle, and the reaction is 10 min;

[0091] (4) the material in the vertical reaction kettle enters the horizontal reaction kettle, the horizontal reaction kettle adopts screw propelling type rotary stirring, the temperature is 150°C, the reaction time is 60 min, a certain amount of gas is discharged after the reaction is completed, and the water content in the system at this time is 9.30%.

[0092] (5) after the reaction product is cooled to 100°C, it enters the neutralization reaction kettle, and is neutralized with ammonia to adjust the pH value of the product to 4;

[0093] (6) The mineral fertilizer obtained has a free water content of 4.64%, and the effective component content is 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 feldspar-like material with a silicon-oxygen and aluminum-oxygen tetrahedral framework structure content of 11.61%.

[0094] Comparative Example 4, no ammonium sulfate is added in this example, and the decomposition rate of the phosphate rock has little effect, but the potassium extraction rate is reduced, the main reason is that the addition of ammonium sulfate can improve the solubility of calcium sulfate, that is, increase the calcium ion concentration in the system, thereby improving the ability to displace potassium ions in potassium feldspar, that is, improving the potassium extraction rate.

[0095] Example 8

[0096] (1) 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 are uniformly mixed to obtain a wet material;

[0097] (2) The wet material is continuously injected into a vertical reaction kettle, and the vertical reaction kettle is subjected to strong stirring by a stirring paddle driving a ball mill;

[0098] (3) 40 parts of concentrated sulfuric acid are continuously pumped into the vertical reaction kettle, and the reaction is carried out for 10 min;

[0099] (4) The material in the vertical reaction kettle is transferred to a horizontal reaction kettle, the horizontal reaction kettle is subjected to rotary stirring by a screw propelling, the temperature is 200°C, the reaction time is 60 min, and a certain amount of gas is discharged after the reaction is completed, at this time, the water content in the system is 8.33%.

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

[0101] (6) The mineral fertilizer obtained has a free water content of 3.93%, and the effective component content is 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 feldspar-like material with a silicon-oxygen and aluminum-oxygen tetrahedral framework structure content of 10.99%.

[0102] Compared with Comparative Example 4, the temperature in the horizontal reactor is increased in this example, and the extraction rates of phosphorus and calcium change little, but the extraction rate of potassium increases greatly. The main reason is that the increase of temperature increases the ion energy in the system, and the ability of potassium ion exchange in potassium feldspar is enhanced, thereby increasing the extraction rate of potassium. When the temperature exceeds 200℃, the system pressure will exceed 1.6 MPa, which belongs to the medium pressure range, and the industrialization engineering design requirements will be increased; in addition, the reaction heat of the system will naturally heat the system materials to 150℃ and above, therefore, the temperature range of the present application is set to 150℃-200℃.

[0103] Example 9

[0104] Fertilizer efficiency test was carried out on small green vegetables, and then rotary tillage was carried out. 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 applied per mu; treatment 2: 30 kg of mineral fertilizer after cooling in Example 4 was applied per mu. The relevant detection structure at the time of small green vegetable harvesting is as follows:

[0105] (1) Small green vegetable leaf chlorophyll balance value (detected before harvesting at about 10 o'clock in the morning): the average value of chlorophyll of treatment 1 was 46.56 (SPAD), and the average value of chlorophyll of treatment 2 was 49.6 (SPAD);

[0106] (2) Average weight of equal diameter (80 mm) area leaf: 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 void ratio: the soil void ratio before fertilization was 32%, and after the harvesting of small green vegetables, the soil void ratio of treatment 1 was 33%, and the soil void ratio of treatment 2 was 46%.

[0110] Compared with N-P2O5-K2O = 15-15-15 compound fertilizer, the mineral fertilizer obtained in Example 4 has good yield-increasing, quality-improving and soil-loosening effects. The main reason is that the mineral fertilizer obtained in Example 4 not only contains a large amount of various mineral elements, but also contains potassium feldspar, sodium feldspar, calcium feldspar and magnesium feldspar with silicate and aluminate tetrahedral framework structure, which can promote soil loosening.

[0111] Example 10

[0112] The example is operated according to the operation process of Example 1, with the difference that the wet material is 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; the amount of sulfuric acid is changed (30 parts, 35 parts, 40 parts, 45 parts, and 50 parts, respectively), and five groups of mineral fertilizers are prepared. The experimental results are shown in Table 1. Figure 2 The optimal amount of concentrated sulfuric acid is about 38 kg; the main component contents of the phosphate rock powder and the potassium feldspar powder in this experiment are shown in Table 1.

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

[0114] Mineral powder Item Content / % Item Content / % Phosphate rock powder P2O5 15.62 Ca 19.76 Potassium feldspar powder K2O 9.69

[0115] Example 11

[0116] The example is operated according to the operation process of Example 1, with the difference that the wet material is 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, and 35 parts of water; the amount of sulfuric acid is changed (40 parts, 45 parts, 50 parts, 55 parts, and 60 parts, respectively), and five groups of mineral fertilizers are prepared. The experimental results are shown in Table 2. Figure 3 The optimal amount of concentrated sulfuric acid is about 50 kg; the main component contents of the phosphate rock powder and the potassium feldspar powder in this experiment are shown in Table 2.

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

[0118] Mineral powder Item Content / % Item Content / % Phosphate rock powder P2O5 19.28 Ca 26.04 Potassium feldspar powder K2O 9.69

[0119] Example 12

[0120] The example is operated according to the operation process of Example 1, with the difference that the wet material is 100 parts of phosphate rock powder, 50 parts of potassium feldspar powder, and 35 parts of water; the amount of sulfuric acid is changed (50 parts, 55 parts, 60 parts, 65 parts, and 70 parts, respectively), and five groups of mineral fertilizers are prepared. The experimental results are shown in Table 3. Figure 4 The optimal amount of concentrated sulfuric acid is about 59 kg; the main component contents of the phosphate rock powder and the potassium feldspar powder in this experiment are shown in Table 3.

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

[0122] Mineral powder Item Content / % Item Content / % Phosphate rock powder P2O5 24.9 Ca 31.27 Potassium feldspar powder K2O 9.69

[0123] As can be seen from Table 1, Figures 2-4 with the increase of the amount of sulfuric acid, the phosphorus extraction rate gradually increases, and the potassium extraction presents a parabolic shape of first increasing and then decreasing. This is because phosphorus is extracted with the decomposition of phosphate rock by sulfuric acid, while potassium is mainly replaced by ions with a smaller ionic radius than K + (such as Ca 2+ , etc.) in the potassium feldspar to K +Ions. Because Ca in the reaction system 2+ The amount of plasma present determines the potassium extraction rate. The products of sulfuric acid decomposition of phosphate rock include slightly soluble calcium sulfate and phosphoric acid. Phosphoric acid can also participate in the decomposition of phosphate rock to form water-soluble calcium dihydrogen phosphate. When the amount of sulfuric acid is too small, the phosphate rock decomposition is incomplete, resulting in a low amount of soluble calcium dihydrogen phosphate in the system, meaning a low amount of calcium ions in the solution and a low potassium extraction rate. When the amount of sulfuric acid is too large, although the phosphate rock decomposition is relatively complete, the excess sulfuric acid will combine with calcium ions in the solution to form slightly soluble calcium sulfate, which greatly reduces the amount of calcium ions in the solution, leading to a lower potassium extraction rate. It is evident that there is an optimal range for the amount of sulfuric acid used. Since the amount of other cations in phosphate rock that react with sulfuric and phosphoric acids is much smaller than that of calcium ions, this optimal range primarily depends on the calcium (Ca) and phosphorus (P₂O₅) content in the phosphate rock powder. The optimal range for sulfuric acid usage should satisfy the following condition: the amount of calcium in the phosphate rock equals the sum of the amount of P₂O₅ in the phosphate rock and the amount of concentrated sulfuric acid added. Theoretical calculations may deviate slightly from actual experimental results because different phosphate rocks also contain small amounts of elements such as magnesium, sodium, and iron, which also consume sulfuric acid. The amount of Mg in these elements... 2+ Na + The ionic radii are all less than K. + Fluorine also participates in potassium ion exchange in potassium feldspar; additionally, phosphate rock contains a small amount of fluorine, which can decompose potassium feldspar to release potassium. However, the content of these elements is very small, and their impact on sulfuric acid consumption is minimal. Therefore, the deviation in sulfuric acid usage will not be too large, with a relative error typically not exceeding 5%. The above experimental and theoretical calculation results are shown in Table 4, and... Figures 1-3 The experimental results are basically consistent.

[0124] Table 4. Calculation of Optimal Sulfuric Acid Consumption for Different Phosphate Rock Powders (100kg)

[0125]

[0126] Example 13

[0127] This embodiment follows the operation process of embodiment 4, except that the amount of ammonium sulfate is changed (0 parts, 3 parts, 4 parts, 5 parts, and 6 parts respectively) to prepare 5 groups of mineral fertilizers.

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

[0129] Example 14

[0130] This embodiment follows the operation process of embodiment 4, except that the amount of borax is changed (0 parts, 1.2 parts, 2.4 parts, 4.8 parts, and 6.0 parts respectively) to prepare 5 groups of mineral fertilizers.

[0131] Depend on Figure 6 It can be seen that borax has little effect on phosphorus extraction rate, but it has a certain impact on potassium extraction rate. The potassium extraction rate increases with increasing borax dosage. In this experimental system, after the borax dosage reached 4.8 parts, further increases in borax dosage resulted in only a small increase in potassium extraction rate. The reason why adding borax can improve potassium extraction rate is that borax contains 12% sodium ions. The radius of sodium ions is much smaller than that of potassium ions, and under certain conditions, it easily displaces potassium ions from potassium feldspar, thereby improving potassium extraction rate.

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

Claims

1. A method for preparing mineral fertilizer using medium- and low-grade phosphate rock and potassium feldspar, characterized in that, Includes the following steps: S1, mix phosphate rock powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate, and water evenly to obtain a wet material, and control the moisture content to ≤20%; S2, the obtained wet material is continuously injected into the vertical reactor, and the reactor uses a stirring paddle to drive the ball mill to strongly stir the material; S3, concentrated sulfuric acid is continuously pumped into the vertical reactor to react rapidly with the wet phosphate rock; S4, the material from the vertical reactor is then fed into the horizontal reactor to continue the decomposition of phosphate rock and the extraction of potassium from potassium feldspar. The horizontal reactor uses a screw propulsion rotary agitator, and exhaust is performed after the reaction is completed. S5, the reaction product after exhaust is cooled to 80-100℃ and then enters the neutralization reactor. The pH value of the product is adjusted to 3-9 by neutralization with ammonia to obtain the neutralized product. S6, after the neutralization product is cooled to room temperature, yields a mineral fertilizer with a free water content ≤5.0%; In step S1, the mass parts of phosphate rock powder, potassium feldspar powder, borax, zinc sulfate, ammonium molybdate, ammonium sulfate, and water are as follows: 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. In step S3, the amount of concentrated sulfuric acid pumped in meets 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, wherein the concentrated sulfuric acid is 98% H2SO4. In step S3, the mass fraction of concentrated sulfuric acid pumped in is 35-65 parts. In step S4, the reaction temperature is 150-200℃ and the reaction time is 30-60 min. Before proceeding to step S5, the gas is first discharged until the water content of the system is ≤10%.

2. The method for preparing mineral fertilizer using medium- and low-grade phosphate rock and potassium feldspar as described in claim 1, characterized in that, In step S1, the phosphate rock powder passes through a 100-mesh standard sieve, and the potassium feldspar powder passes through a 200-mesh standard sieve.

3. The method for preparing mineral fertilizer using medium- and low-grade phosphate rock and potassium feldspar as described in claim 1, characterized in that, In step S3, the reaction time is 5-10 minutes.

4. The method for preparing mineral fertilizer using medium- and low-grade phosphate rock and potassium feldspar as described in claim 1, characterized in that, In step S5, when mineral fertilizers are applied to alkaline soils, the pH value of the product is adjusted to 3-6.

5. The method for preparing mineral fertilizer using medium- and low-grade phosphate rock and potassium feldspar as described in claim 1, characterized in that, In step S5, when mineral fertilizers are applied to acidic soils, the pH value of the product is adjusted to 7-9.

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