S-NPK production system and method

Abstract

The invention discloses an S-NPK production system and method.The S-NPK production system comprises an acid mixing tank, a tubular reactor, a neutralizing tank, a granulation drying machine, a classifying screen and a crusher, potassium hydrogen sulfate and phosphoric acid are mixed in the acid mixing tank to prepare mixed acid, the mixed acid reacts with ammonia, then slurry is prepared in the neutralizing tank again, and then the mixed acid reacts with the ammonia to prepare the S-NPK. And spraying the slurry into a granulating and drying machine by using a slurry spray gun for granulating and drying, screening granular materials in the granulating and drying machine, and taking qualified materials after screening as a target product, namely S-NPK. According to the invention, potassium bisulfate with relatively low cost is used for replacing potassium sulfate with high energy consumption, pollution and selling price to produce chlorine-free high-concentration S-NPK, phosphoric acid and slurry do not need to be concentrated, the external return material ratio is low, the nutrient content is complete, the defects of single-nutrient or dual-nutrient fertilizer are overcome, the problem that the fertilizer application requirement of crops is not met is solved, the fertilizer application workload is reduced, the crop yield is increased, and the economic benefit is increased. The fertilizer application effect is improved.

Description

Technical Field

[0001] The present invention relates to a production system and method of S-NPK, belonging to the technical field of chemical production. Background Art

[0002] The nutrients required for plant growth are mainly supplied by soil and fertilizer. Based on the three physiological characteristics of essential plant nutrients, namely: (1) they have a direct effect on plant growth or physiological metabolism; (2) if any one of these elements is lacking, the plant cannot grow and develop normally; and (3) their physiological functions cannot be replaced by other elements, there are 16 essential nutrients for plant growth, including nitrogen (N), phosphorus (P), potassium (K), and sulfur (S).

[0003] Nitrogen is a component of many organic compounds in plants, including proteins, nucleic acids, chlorophyll, enzymes, vitamins, alkaloids, and hormones. Phosphorus is second only to nitrogen in its content in crop seeds. It also contributes to drought, cold, and disease resistance, and early maturity. Potassium, in its ionic form, participates in physiological and biochemical processes in plants. For example, potassium activates enzymes, accelerates various metabolic processes, promotes ATP synthesis, and accelerates photosynthesis and the transfer of its products (such as sugars and starch), thereby improving crop yield and quality. Sulfur, present in plants at a similar level to phosphorus, is a component of important compounds such as proteins, enzymes, and vitamin B1, surpassing only nitrogen, phosphorus, and potassium in importance. Cruciferous crops contain high levels of sulfur, and sulfur deficiency can affect their growth, leading to reduced yield and quality.

[0004] The low levels of available nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) in the soil often become the main factor limiting plant yields, requiring fertilization to replenish them. Currently produced ammonium phosphate compound fertilizers are essentially monoammonium phosphate and / or diammonium phosphate (hereinafter referred to as ammonium phosphate). While ammonium phosphate has a mature production process and high nutrient content, it can be used directly as fertilizer. However, both monoammonium phosphate and diammonium phosphate contain no potassium or sulfur, and therefore cannot meet crop needs. Summary of the Invention

[0005] The object of the present invention is to provide a S-NPK production system and method for producing S-NPK fertilizer containing nitrogen, phosphorus, potassium and sulfur to better meet the needs of crops.

[0006] The S-NPK production system of the present invention adopts the following technical solution: a S-NPK production system, which includes a mixed acid tank, a tubular reactor, a neutralization tank, a granulation dryer, a grading screen and a crusher, wherein the upper portion of the mixed acid tank is provided with a phosphoric acid inlet and a potassium bisulfate inlet, the lower portion of the mixed acid tank is provided with a mixed acid outlet, the two ends of the tubular reactor are respectively an ammonia inlet and a slurry outlet, the side of the tubular reactor near the ammonia inlet is provided with a mixed acid inlet, the mixed acid inlet of the tubular reactor is connected to the mixed acid outlet of the mixed acid tank, the neutralization tank is provided with a slurry inlet, an ammonia inlet and a neutralized slurry outlet, the slurry inlet of the neutralization tank is connected to the slurry outlet of the tubular reactor, and the slurry spray gun includes A central tube and an outer tube are arranged together inside and outside, and the inlet ends of the central tube and the outer tube are both located outside the granulation dryer, and the outlet ends of the central tube and the outer tube are both located inside the granulation dryer. A compressed air inlet is provided on the wall of the outer tube near the inlet end, and the outlet end of the outer tube is used to spray compressed air. The inlet end of the central tube is connected with the slurry outlet of the neutralization tank, and the outlet end of the central tube is used to spray slurry. The material outlet of the granulation dryer is connected with the material inlet of the grading screen. The grading screen is provided with a coarse particle outlet, a qualified particle outlet and a fine particle outlet from top to bottom. The coarse particle outlet is connected with the material inlet of the crusher, and the fine particle outlet and the material outlet of the crusher are both connected with the material inlet of the granulation dryer.

[0007] The qualified particle outlet is connected to a finished product conveyor; a granular material elevator is provided between the material outlet of the granulation dryer and the material inlet of the grading screen; a return material conveyor is provided at the material inlet of the granulation dryer, the fine particle outlet of the grading screen and the material outlet of the crusher are both connected to the inlet of the return material conveyor, and the outlet of the return material conveyor is connected to the material inlet of the granulation dryer.

[0008] The central tube outlet end and the outer tube outlet end of the slurry spray gun are both gradually shrinking tapered openings; and the end faces of the central tube outlet end and the outer tube outlet end are flush; the angle of the tapered opening of the central tube outlet end is γ, 35º≥γ≥25º; the neutralization tank adopts a structure with a large upper section cross-sectional area and a small lower section cross-sectional area.

[0009] The granulation dryer includes a drum and a front sealed cabinet and a rear sealed cabinet respectively arranged at the front and rear ends of the drum. The drum is inclined downward from front to back. The material inlet of the granulation dryer is arranged at the top of the front sealed cabinet, and the material outlet of the granulation dryer is arranged at the bottom of the rear sealed cabinet. A return material feed pipe is provided in the material inlet of the granulation dryer, and the lower end of the return material feed pipe is an inclined pipe inclined toward the inside of the drum. A hot air inlet is provided on the side of the front sealed cabinet, and an exhaust gas outlet is provided on the top of the rear sealed cabinet. A rotary drum screen is provided in the rear sealed cabinet.

[0010] The front sealed cabinet contains the feeding area, the rear sealed cabinet contains the screening area, the drum contains the material guiding area, the granulating area, the drying area and the area without shoveling plate in sequence from the front sealed cabinet to the rear sealed cabinet, the drum is provided with feeding inclined plates on the inner wall of the material guiding area, the feeding inclined plates are inclined; a material baffle is provided between the granulating area and the drying area, shoveling plates are provided in the granulating area and the drying area, a material dividing slope is provided near the screening area in the area without shoveling plate, and the inner diameter of the material dividing slope decreases and then increases from the feeding area to the screening area.

[0011] There are more than two groups of scavenging plates, and each group of scavenging plates includes a first scavenging plate, a second scavenging plate, and a third scavenging plate distributed in sequence from the feeding area to the screening area. The first scavenging plate is a straight plate structure evenly distributed on the circumference of the inner wall of the drum, the second scavenging plate is a bent plate structure with a primary bend evenly distributed on the circumference of the inner wall of the drum, and the third scavenging plate is a bent plate structure with a secondary bend evenly distributed on the circumference of the inner wall of the drum. The bending direction of the second and third scavenging plates is the same as the rotation direction of the drum.

[0012] Two square return tubes with square cross-sections are provided in the drum. The two square return tubes are both arranged on the inner wall of the drum. The inlets of the two square return tubes are both located at the starting point of the material distribution slope, and the outlets of the two square return tubes are both located in the material guide area; the two square return tubes extend in a spiral shape, and the two square return tubes are arranged axially symmetrically with the center line of the drum.

[0013] The angle between the axis of the drum and the horizontal direction is α, 4°≥α≥0.5°; the feed inclined plate forms an angle of 10°~15° with the center line of the drum, and each shoveling plate is parallel to the axis of the drum; the material distribution slope is located at the end of the non-shoveling plate area, and the angle between the material distribution slope and the inner wall of the drum is β, 40°≥β≥30°, and the maximum height of the material distribution slope in the radial direction of the drum is Hx; the rotary screen is located at the very end of the drum and connected to the material distribution slope, and the mesh size of the rotary screen is 40×40mm; the material baffle is located in the middle of the drum, and its height in the radial direction of the drum is Hd, Hd>Hx; the distance between the axis of the material inlet and the material outlet of the granulating dryer is L, the drum diameter is D, L:D=3~4, and the drum speed is 3~6r / min.

[0014] The production method of S-NPK of the present invention adopts the following technical scheme: A production method of S-NPK, which is carried out by adopting the above-mentioned S-NPK production system, and comprises the following steps: (1) raw material feeding and S-NPK preparation section: potassium bisulfate and phosphoric acid from the boundary zone are introduced into a mixed acid tank, the potassium bisulfate contains KHSO4 with a mass concentration of 80% to 90%, and the phosphoric acid contains P2O5 with a mass concentration of 20% to 35%, and the potassium bisulfate and phosphoric acid are fully stirred and mixed by a mixed acid agitator in the mixed acid tank to prepare a mixed acid, and ammonia from the boundary zone and the mixed acid prepared in the mixed acid tank are introduced into a tubular reactor, and ammonia and the mixed acid react in the tubular reactor to generate S-NPK slurry, and the molar ratio of ammonia to phosphoric acid in the S-NPK slurry is NH3:H3PO4=10~13:10, and the S-NPK slurry after the reaction in the tubular reactor and the ammonia from the boundary zone are introduced into the mixed acid agitator. The S-NPK slurry is reacted with ammonia in the neutralization tank to generate S-NPK slurry. The molar ratio of ammonia to phosphoric acid in the slurry is NH3:H3PO4=14~17:10, and the mass percentage of H2O is 25~35%. The S-NPK slurry after the reaction in the neutralization tank is passed into the slurry spray gun; (2) S-NPK spray granulation drying section: The S-NPK slurry from the neutralization tank enters the central tube of the slurry spray gun, and the compressed air from the boundary zone enters between the outer tube and the central tube of the slurry spray gun. Under the action of the compressed air, the S-NPK slurry is atomized and sprayed into the granulation dryer. After atomization, the S-NPK slurry forms granular material under the action of the granulation dryer. The granular material is discharged from the material outlet of the granulation dryer and enters the grading screen; (3) S-NPK screening and discharging section: The granular S-NPK material from the granulation dryer is graded on the grading screen, and the particle size is greater than 4mm. The S-NPK coarse particles are discharged from the coarse particle outlet through the grading screen, and then enter the crusher for crushing. The crushed materials are returned to the granulation dryer as external return materials; the S-NPK fine particles with a particle size of less than 2mm are discharged from the grading screen through the fine particle outlet, and then returned to the granulation dryer as external return materials; the S-NPK qualified particles with a particle size of 2-4mm are discharged from the qualified particle outlet through the grading screen as the target product - S-NPK.

[0015] The S-NPK spray granulation drying process of step (2) is as follows: the S-NPK slurry is atomized by a spray gun and sprayed on the material curtain lifted by the shoveling plate, and dried with hot air at 250℃~320℃; as the granulation dryer drum rotates, the external return material from the material inlet and the internal return material from the square return pipe are all added to the material guide area, and the return material is introduced into the granulation area by the feed inclined plate to provide S-NPK solid particles for the material curtain. The S-NPK solid particles are repeatedly coated, granulated and dried and move from the granulation area to the drying area and the non-shoveling plate area. In the non-shoveling plate area, large particles cross the material separation slope and enter the screening area, and fine particles are deposited on the material separation slope. The large particles entering the screening area are screened by a drum screen, and the oversized particles with a particle size greater than 40 mm are left in the screening area and picked out regularly. The large particles S-NPK with a particle size less than 40 mm are discharged from the granulation dryer from the material outlet as the discharge material. The discharged S-NPK particles contain 1% to 2% by mass of H2O; the ratio of internal return material to discharge material is 2 to 4:1; the ratio of external return material to target product is 5 to 15:10; the target product contains 1% to 2% by mass of water, and the molar ratio of ammonia to phosphoric acid is NH3:H3PO4=14 to 17:10.

[0016] The present invention has the following beneficial effects: A mixed acid is prepared by mixing potassium bisulfate and phosphoric acid, which is then neutralized with ammonia to produce a slurry. The slurry produced by neutralizing the mixed acid with ammonia can be used directly to produce S-NPK without concentration. The slurry is then sprayed directly into a granulation dryer using a slurry spray gun for granulation and drying. The granulation dryer integrates granulation and drying functions, making it a highly efficient, energy-saving, and multifunctional device. The granulated material produced by the granulation dryer is screened, and qualified material is used as the target product, S-NPK (sulfur-based compound fertilizer). The present invention replaces potassium sulfate, which is energy-consuming, polluting, and expensive, with low-cost potassium bisulfate to produce chlorine-free, high-concentration S-NPK (sulfur-based compound fertilizer). During the production process, neither the phosphoric acid nor the slurry requires concentration, resulting in a low return ratio (0.5-1.5) and a comprehensive nutrient content. This addresses the shortcomings of single-nutrient or dual-nutrient fertilizers that do not meet crop fertilization requirements, reduces fertilization workload, increases crop yields, and improves the effectiveness of chemical fertilizer application.

[0017] Preferably, the slurry spray gun uses a two-stream external mixing spray gun with a spray angle of 35°≥γ≥25°. Due to the small spray angle, the slurry droplets are less likely to scatter onto the inner wall of the granulation dryer and cause scarring. The atomized slurry is evenly coated on the surface of the solid particles in the material curtain. After the moisture is rapidly vaporized in the hot air, it is re-coated. After repeated coating and vaporization processes, the fine particles gradually grow into qualified particles. The coated granules have a smooth surface, high mechanical strength, and good appearance. The lower section of the neutralization tank has a smaller cross-section, making the mixing here more effective. The upper section has a larger cross-section, which has a buffering effect on boiling and bubbling, while also providing a sufficient space for gas-liquid separation.

[0018] As a preferred method, a feed ramp is installed at the front end of the inner wall of the granulation dryer drum, which can smoothly guide the internal and external return materials into the drum; three different scooping plates are installed at the rear end of the feed ramp to scoop up the materials in the drum, and each scooping plate scatters the materials in turn, thereby forming a complete and continuous material curtain in the drum; the rear end of the scooping plate is a smooth cylinder without a scooping plate, which can reduce the loss caused by dust generated when the dry material is lifted and scattered and carried away by the exhaust gas; a material dividing slope is installed at the tail end of the smooth cylinder without a scooping plate as an internal grading device, and the fine particles after the large particles are overflowed after classification are sorted and discharged through an axisymmetric arrangement along the inner wall of the drum. The two square return pipes return to the material guide area of the granulation dryer, reducing external return material (when there is no internal return material, the external return material is 4 to 6 times the target product; when there is internal return material, the external return material is 0.5 to 1.5 times the target product) and dust. The load of the external return material equipment is greatly reduced, energy consumption is reduced, and the operating environment is improved; the granulation area and the drying area are separated by an annular material baffle, so that the granulation area maintains a large filling coefficient; a rotary screen with a mesh size of 40×40mm is installed at the end of the drum to separate materials with a diameter greater than 40mm to prevent them from entering the granular material elevator and clogging the bucket. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a production system for S-NPK according to an embodiment of the present invention; Figure 2 for Figure 1 Schematic diagram of the medium slurry spray gun; Figure 3 for Figure 1 Front view of the medium granulation dryer; Figure 4 for Figure 1 Schematic diagram of the cross section of the medium granulation dryer; Figure 5 for Figure 4 Schematic diagram of the middle AA section; Figure 6 for Figure 4 Schematic diagram of the middle BB section; Figure 7 for Figure 4 Schematic diagram of the middle CC section; Figure 8 for Figure 4 Schematic diagram of the middle EE section; Figure 9 for Figure 3 and Figure 4 Schematic diagram of the FF cross section; Figure 10 for Figure 3 and Figure 4 Schematic diagram of the middle GG section; Figure 11This is a performance evaluation result table of a 15 t / h S-NPK system of an application example of the present invention.

[0020] Among them, 1. Mixed acid tank, 2. Mixed acid agitator, 3. Mixed acid delivery pump, 4. Tubular reactor, 5. Neutralization tank, 6. Slurry delivery pump, 7. Slurry spray gun, 7-1. Center pipe, 7-2. Compressed air inlet, 7-3. Outer pipe, 8. Granulating dryer, 8-1. Front sealing cabinet, 8-2. External return material feed pipe, 8-3. Front roller, 8-4. Transmission gear, 8-5. Rear roller, 8-6. Square return pipe, 8-7. Material baffle , 8-8, material distribution slope, 8-9, rotary drum screen, 8-10, rear sealing cabinet, 8-11, feed inclined plate, 8-12, first material copying plate, 8-13, second material copying plate, 8-14, third material copying plate, 8-15, drum, 9, granular material elevator, 10, grading screen, 10-1, coarse particle outlet, 10-2, qualified particle outlet, 10-3, fine particle outlet, 11, finished product conveyor, 12, crusher, 13, return material conveyor. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The technical solutions in the embodiments of this patent will be clearly and completely described below in conjunction with the drawings in the embodiments of this patent. Obviously, the described embodiments are part of the embodiments of this patent, not all of the embodiments. The components of the embodiments of this patent generally described and shown in the drawings herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this patent provided in the drawings is not intended to limit the scope of the patent claimed for protection, but merely represents selected embodiments of this patent. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this patent.

[0023] like Figure 1As shown, a production system of S-NPK according to an embodiment of the present invention comprises a mixed acid tank 1, a tubular reactor 4, a neutralization tank 5, a granulation dryer 8, a grading screen 10 and a crusher 12, wherein the upper portion of the mixed acid tank 1 is provided with a phosphoric acid inlet and a potassium bisulfate inlet, the lower portion of the mixed acid tank 1 is provided with a mixed acid outlet, the two ends of the tubular reactor 4 are respectively provided with an ammonia inlet and a slurry outlet, the side of the tubular reactor 4 near the ammonia inlet is provided with a mixed acid inlet, the mixed acid inlet of the tubular reactor 4 is connected to the mixed acid outlet of the mixed acid tank 1, the neutralization tank 5 is provided with a slurry inlet, an ammonia inlet and a neutralized slurry outlet, the slurry inlet of the neutralization tank 5 is connected to the slurry outlet of the tubular reactor 4, the slurry spray gun 7 comprises a central tube 7-1 and an outer tube 7-3 which are arranged together inside and outside, the central tube 7-1 and the outer tube 7-3 are provided together. -3's inlet ends are both located outside the granulation dryer 8, and the outlet ends of the central tube 7-1 and the outer tube 7-3 are both located inside the granulation dryer 8. A compressed air inlet 7-2 is provided on the wall of the outer tube 7-3 near the inlet end, and the outlet end of the outer tube 7-3 is used to spray compressed air. The inlet end of the central tube 7-1 is connected to the slurry outlet of the neutralization tank 5, and the outlet end of the central tube 7-1 is used to spray slurry. The material outlet of the granulation dryer 8 is connected to the material inlet of the grading screen 10. The grading screen 10 is provided with a coarse particle outlet 10-1, a qualified particle outlet 10-2 and a fine particle outlet 10-3 from top to bottom. The coarse particle outlet 10-1 is connected to the material inlet of the crusher 12, and the fine particle outlet 10-3 and the material outlet of the crusher 12 are both connected to the material inlet of the granulation dryer 8.

[0024] The qualified particle outlet 10-2 is connected to a finished product conveyor 11; a granular material elevator 9 is provided between the material outlet of the granulation dryer 8 and the material inlet of the grading screen 10; a return conveyor 13 is provided at the material inlet of the granulation dryer 8, and the fine particle outlet 10-3 of the grading screen 10 and the material outlet of the crusher 12 are both connected to the inlet of the return conveyor 13, and the outlet of the return conveyor 13 is connected to the material inlet of the granulation dryer 8.

[0025] like Figure 2 As shown, the outlet end of the central tube 7-1 and the outlet end of the outer tube 7-3 of the slurry spray gun 7 are both tapered and gradually contract; the end faces of the outlet end of the central tube 7-1 and the outlet end of the outer tube 7-3 are flush; the angle of the tapered outlet end of the central tube 7-1 is γ, 35°≥γ≥25°. The neutralization tank 5 adopts a structure with a large upper section and a small lower section. The structure of the granulation dryer 8 is as follows Figures 3 to 10As shown, the granulation dryer 8 includes a drum 8-15 and a front sealed cabinet 8-1 and a rear sealed cabinet 8-10 respectively arranged at the front and rear ends of the drum 8-15, the drum 8-15 is inclined downward from front to back, the material inlet of the granulation dryer 8 is arranged at the top of the front sealed cabinet 8-1, and the material outlet of the granulation dryer 8 is arranged at the bottom of the rear sealed cabinet 8-10. A return feed pipe 8-2 is provided in the material inlet of the granulation dryer 8, and the lower end of the return feed pipe 8-2 is an inclined pipe inclined toward the inside of the drum 8-15. A hot air inlet is provided on the side of the front sealed cabinet 8-1, and an exhaust gas outlet is provided at the top of the rear sealed cabinet 8-10. A rotary drum screen 8-9 is provided in the rear sealed cabinet 8-10.

[0026] The front sealed cabinet 8-1 is the feeding area, the rear sealed cabinet 8-10 is the screening area, the drum 8-15 is the material guide area, the granulation area, the drying area, and the non-copying area from the front sealed cabinet 8-1 to the rear sealed cabinet 8-10. The drum 8-15 is provided with a feed inclined plate 8-11 on the inner wall of the material guide area. The feed inclined plate 8-11 is tilted and forms an angle of 10° to 15° with the center line of the drum. The structure of the feed inclined plate is as follows: Figure 5 As shown; a material baffle 8-7 is provided between the granulation zone and the drying zone, a shoveling plate is provided in the granulation zone and the drying zone, and a material dividing slope 8-8 is provided near the screening zone in the area without a shoveling plate. The inner diameter of the material dividing slope 8-8 decreases and then increases from the feed zone to the screening zone.

[0027] There are more than two groups of scissor plates, each group of scissor plates includes a first scissor plate 8-12, a second scissor plate 8-13, and a third scissor plate 8-14 distributed in sequence from the feeding area to the screening area, and their structures are as follows: Figures 6 to 8 As shown, the first scavenging plate 8-12 is a straight plate structure evenly distributed on the circumference of the inner wall of the roller 8-15, the second scavenging plate 8-13 is a bent plate structure with a primary bend evenly distributed on the circumference of the inner wall of the roller 8-15, and the third scavenging plate 8-14 is a bent plate structure with a secondary bend evenly distributed on the circumference of the inner wall of the roller 8-15. The bending direction of the second scavenging plate 8-13 and the third scavenging plate 8-14 is the same as the rotation direction of the roller 8-15.

[0028] Two square return tubes 8-6 with square cross-sections are provided in the roller 8-15. The two square return tubes 8-6 are both arranged on the inner wall of the roller. The inlets of the two square return tubes are both located at the starting point of the material distribution slope 8-8, and the outlets of the two square return tubes are both located in the material guide area; the two square return tubes 8-6 extend in a spiral shape, and the two square return tubes 8-6 are arranged axially symmetrically with the center line of the roller 8-15. Figure 3 and Figure 4 Only the cross-sectional structure is shown, and only half of each square return tube is shown.

[0029] The angle between the axis of the roller 8-15 and the horizontal direction is α, 4°≥α≥0.5°; the feed inclined plate 8-11 forms an angle of 10°~15° with the center line of the roller 8-15, and each copying plate is parallel to the axis of the roller 8-15; the material dividing slope 8-8 is located at the end of the non-copying plate area, and the angle between the material dividing slope 8-8 and the inner wall of the roller 8-15 is β, 40°≥β≥30°, and the maximum height of the material dividing slope 8-8 in the radial direction of the roller 8-15 is Hx; The rotary screen 8-9 is located at the very end of the drum 8-15 and is connected to the material distribution slope 8-8. The sieve size of the rotary screen 8-9 is 40×40 mm; the material baffle 8-7 is located in the middle of the drum 8-15, and its height in the radial direction of the drum 8-15 is Hd, Hd>Hx; the distance between the material inlet and the material outlet axis of the granulating dryer 8 is L, the diameter of the drum 8-15 is D, L:D=3~4, and the rotation speed of the drum 8-15 is 3~6r / min.

[0030] The production method of S-NPK according to one embodiment of the present invention is carried out using the above-mentioned S-NPK production system, and comprises the following steps: (1) Raw material feeding and S-NPK preparation section: potassium bisulfate and phosphoric acid from the boundary zone are introduced into the mixed acid tank 1, wherein the potassium bisulfate contains KHSO4 with a mass concentration of 80% to 90%, and the potassium bisulfate comes from the potassium bisulfate preparation section; the phosphoric acid contains P2O5 with a mass concentration of 20% to 35%, and the phosphoric acid comes from the boundary zone; the potassium bisulfate and the phosphoric acid are fully stirred and mixed by the mixed acid stirrer 2 in the mixed acid tank 1 to obtain mixed acid; the mixed acid is transported by the mixed acid pump 3; the ammonia from the boundary zone and the mixed acid prepared in the mixed acid tank 1 are introduced into the tubular reactor 4, and the ammonia reacts with the mixed acid in the tubular reactor 4 Generate an S-NPK slurry, wherein the molar ratio of ammonia to phosphoric acid in the S-NPK slurry is NH3:H3PO4=10-13:10, pass the S-NPK slurry after the reaction in the tubular reactor 4 and the ammonia from the boundary zone into the neutralization tank 5, and react with the ammonia in the neutralization tank 5 to continue to generate an S-NPK slurry, wherein the molar ratio of ammonia to phosphoric acid in the slurry is NH3:H3PO4=14-17:10 and the mass percentage of H2O is 25-35%, and the S-NPK slurry after the reaction in the neutralization tank 5 is passed into the slurry spray gun 7 by using the slurry delivery pump 6; (2) S-NPK spraying granulation and drying section: The S-NPK slurry from the neutralization tank 5 enters the central tube 7-1 of the slurry spray gun 7, and the compressed air from the boundary area enters between the outer tube 7-3 and the central tube 7-2 of the slurry spray gun 7 through the compressed air inlet 7-2. Under the action of the compressed air, the S-NPK slurry is atomized and sprayed into the granulation dryer 8. After atomization, the S-NPK slurry is formed into granular material under the action of the granulation dryer 8. The granular material is discharged from the material outlet of the granulation dryer 8 and is lifted to the grading screen 10 by the granular material elevator 9.

[0031] The S-NPK spray granulation drying process of this step is as follows: the S-NPK slurry is discharged from the central tube 7-1, and the compressed air from the boundary area is discharged from the outer tube 7-3 of the slurry spray gun. The S-NPK slurry is atomized by the compressed air and sprayed into the granulation dryer 8 and sprayed on the material curtain lifted by the first scooping plate 8-12, the second scooping plate 8-13, and the third scooping plate 8-14, and dried with hot air at 250°C to 320°C; as the drum 8-15 of the granulation dryer rotates, the external return material from the material inlet and the internal return material of the square return pipe 8-6 are all added to the material guide area, and the return material is introduced into the granulation area by the feed inclined plate 8-11 to provide S-NPK for the material curtain. K solid particles and S-NPK solid particles are repeatedly coated, granulated and dried and move from the granulation area to the drying area and the non-copying plate area. In the non-copying plate area, large particles cross the dividing slope 8-8 and enter the screening area, and fine particles are deposited in front of the dividing slope 8-8 as internal return material and enter the square return pipe 8-6 to return to the material guide area; the large particles entering the screening area are screened by the rotary drum screen 8-9, and the oversized particles with a particle size greater than 40mm are left in the screening area and picked out regularly. The large particles S-NPK with a particle size less than 40mm are discharged from the material outlet of the granulation dryer 8 as the discharge material. The mass percentage of H2O in the discharged S-NPK particles is 1%~2%; the ratio of internal return material to discharge material is 2~4:1.

[0032] (3) S-NPK screening and discharging section: Granular S-NPK material from the granulation dryer is classified on the grading screen 10. S-NPK coarse particles with a particle size greater than 4 mm are discharged from the grading screen 10 through the coarse particle outlet 10-1 and then enter the crusher 12 for crushing. The crushed material is returned to the granulation dryer 8 as external return material. S-NPK fine particles with a particle size less than 2 mm are discharged from the grading screen 10 through the fine particle outlet 10-3 and then returned to the granulation dryer 8 as external return material. The ratio of external return material to target product is 5-15:10. S-NPK qualified particles with a particle size of 2-4 mm are discharged from the grading screen 10 through the qualified particle outlet 10-2 and are the target product - S-NPK (sulfur-based compound fertilizer). The target product contains 1% to 2% water by mass, and the molar ratio of ammonia to phosphoric acid is NH3:H3PO4 = 14-17:10.

[0033] In a specific application example of an S-NPK production system, the feed end of the granulating dryer 8 is high and the discharge end is low, and the angle α between the drum axis and the horizontal direction is 1°; the feed inclined plate 8-11 forms an angle of 12° with the center line of the drum 8-15, the arc angle between two adjacent feed inclined plates 8-11 is 22.5°, the arc angle between two adjacent first scissor plates 8-12 is 22.5°, the arc angle between two adjacent second scissor plates 8-13 is 22.5°, and the arc angle between two adjacent third scissor plates 8-14 is 22.5°. The angle β between the material distribution slope and the inner wall of the drum is 35°, and the height of the highest point of the material distribution slope in the radial direction of the drum 8-15 is Hx=670 mm; the material baffle's radial height in drum 8-15 is Hd = 770 mm; the distance between the material inlet and outlet axes of granulating dryer 8 is L = 16000 mm; the diameter of drum 8-15 is D = 4250 mm; and the speed of drum 8-15 is 4 rpm. When using this application example for S-NPK production, potassium bisulfate comes from the potassium bisulfate preparation section, containing 85% KHSO4 by mass, and phosphoric acid comes from the boundary zone, containing 22% P2O5 by mass. The mass ratio of potassium bisulfate to phosphoric acid entering mixed acid tank 1 is: KHSO4: The mixed acid in the mixed acid tank 1 is delivered to the tubular reactor 4 via the mixed acid delivery pump 3. The molar ratio of ammonia to phosphoric acid in the S-NPK slurry produced in the tubular reactor 4 is 11:10 for NH3:H3PO4. The molar ratio of ammonia to phosphoric acid in the S-NPK slurry produced in the neutralization tank 5 is 16:10 for NH3:H3PO4. The S-NPK slurry produced in the neutralization tank 5 is delivered to the slurry spray gun 7 via the slurry delivery pump 6. In the granulation dryer 8, oversized particles with a particle size greater than 40 mm are retained in the screening area and periodically removed. Large S-NPK particles with a particle size ≤40 mm (containing 1.3% H2O by mass) are discharged as the discharge material. The ratio of internal return material to discharge material is 2:1. The ratio of external return material to target product is 1:1. The molar ratio of ammonia to phosphoric acid is 16:10 for NH3:H3PO4. The target product contains 1.3% by mass of H2O, 10.2% by mass of S, 13.3% by mass of N, 28.5% by mass of P2O5, and 15% by mass of K2O.

[0034] The running result data of this application instance is as follows Figure 11As shown in the table in [1], the target product of this invention, S-NPK, has a total nutrient (N + P2O5 + K2O) weight percentage ≥ 40%, a single nutrient weight percentage ≥ 4%, and a chlorine weight percentage ≤ 3.0%, complying with the national standard GB / T15063-2020. It is a high-concentration compound fertilizer. Chlorine is harmful to crops, causing soil acidification and compaction, salt damage, activating toxic ions, inducing nutrient deficiencies, affecting crop growth and development, and reducing crop quality. The target product of this invention, S-NPK, has a chlorine weight percentage ≤ 3.0%, and can be used as a high-concentration chlorine-free compound fertilizer, complying with the national standard GB / T15063-2020. Compared with existing technologies, the energy consumed to produce the same mass of potassium oxide and potassium sulfate is approximately 23 times that of potassium bisulfate. Using low-cost potassium bisulfate instead of high-cost potassium sulfate to produce the target product, S-NPK, will result in a more affordable price, and the various nutrients can be adjusted according to crop needs.

[0035] In summary, the S-NPK produced by the present invention can make up for the shortcomings of single-nutrient or dual-nutrient fertilizers and the problem that they do not meet the requirements for crop fertilization, reduce the workload of fertilization, increase crop yields, and improve the effect of chemical fertilizer application.

Claims

1. A production system for S-NPK, characterized by: It includes a mixed acid tank, a tubular reactor, a neutralization tank, a granulation dryer, a grading screen and a crusher. The upper part of the mixed acid tank is provided with a phosphoric acid inlet and a potassium bisulfate inlet, the lower part of the mixed acid tank is provided with a mixed acid outlet, the two ends of the tubular reactor are respectively an ammonia inlet and a slurry outlet, the side of the tubular reactor close to the ammonia inlet is provided with a mixed acid inlet, the mixed acid inlet of the tubular reactor is connected with the mixed acid outlet of the mixed acid tank, the neutralization tank is provided with a slurry inlet, an ammonia inlet and a neutralized slurry outlet, the slurry inlet of the neutralization tank is connected with the slurry outlet of the tubular reactor, the slurry spray gun includes a central tube and an outer tube arranged together inside and outside, the central tube The inlet ends of the central tube and the outer tube are both located outside the granulation dryer, and the outlet ends of the central tube and the outer tube are both located inside the granulation dryer. A compressed air inlet is provided on the wall of the outer tube near the inlet end, and the outlet end of the outer tube is used to spray compressed air. The inlet end of the central tube is connected to the slurry outlet of the neutralization tank, and the outlet end of the central tube is used to spray slurry. The material outlet of the granulation dryer is connected to the material inlet of the grading screen. The grading screen is provided with a coarse particle outlet, a qualified particle outlet and a fine particle outlet from top to bottom. The coarse particle outlet is connected to the material inlet of the crusher, and the fine particle outlet and the material outlet of the crusher are both connected to the material inlet of the granulation dryer.

2. The S-NPK production system according to claim 1, wherein: The qualified particle outlet is connected to a finished product conveyor; a granular material elevator is provided between the material outlet of the granulation dryer and the material inlet of the grading screen; a return material conveyor is provided at the material inlet of the granulation dryer, the fine particle outlet of the grading screen and the material outlet of the crusher are both connected to the inlet of the return material conveyor, and the outlet of the return material conveyor is connected to the material inlet of the granulation dryer.

3. The S-NPK production system according to claim 1, wherein: The central tube outlet end and the outer tube outlet end of the slurry spray gun are both gradually shrinking tapered openings; and the end faces of the central tube outlet end and the outer tube outlet end are flush; the angle of the tapered opening of the central tube outlet end is γ, 35º≥γ≥25º; the neutralization tank adopts a structure with a large upper section cross-sectional area and a small lower section cross-sectional area.

4. The S-NPK production system according to claim 1, characterized in that: The granulation dryer includes a drum and a front sealed cabinet and a rear sealed cabinet respectively arranged at the front and rear ends of the drum. The drum is inclined downward from front to back. The material inlet of the granulation dryer is arranged at the top of the front sealed cabinet, and the material outlet of the granulation dryer is arranged at the bottom of the rear sealed cabinet. A return material feed pipe is provided in the material inlet of the granulation dryer, and the lower end of the return material feed pipe is an inclined pipe inclined toward the inside of the drum. A hot air inlet is provided on the side of the front sealed cabinet, and an exhaust gas outlet is provided on the top of the rear sealed cabinet. A rotary drum screen is provided in the rear sealed cabinet.

5. The S-NPK production system according to claim 4, characterized in that: The front sealed cabinet contains the feeding area, the rear sealed cabinet contains the screening area, the drum contains the material guiding area, the granulating area, the drying area and the area without shoveling plate in sequence from the front sealed cabinet to the rear sealed cabinet, the drum is provided with feeding inclined plates on the inner wall of the material guiding area, the feeding inclined plates are inclined; a material baffle is provided between the granulating area and the drying area, shoveling plates are provided in the granulating area and the drying area, a material dividing slope is provided near the screening area in the area without shoveling plate, and the inner diameter of the material dividing slope decreases and then increases from the feeding area to the screening area.

6. The S-NPK production system according to claim 5, characterized in that: There are more than two groups of scavenging plates, and each group of scavenging plates includes a first scavenging plate, a second scavenging plate, and a third scavenging plate distributed in sequence from the feeding area to the screening area. The first scavenging plate is a straight plate structure evenly distributed on the circumference of the inner wall of the drum, the second scavenging plate is a bent plate structure with a primary bend evenly distributed on the circumference of the inner wall of the drum, and the third scavenging plate is a bent plate structure with a secondary bend evenly distributed on the circumference of the inner wall of the drum. The bending direction of the second and third scavenging plates is the same as the rotation direction of the drum.

7. The S-NPK production system according to claim 4, characterized in that: Two square return tubes with square cross-sections are provided in the drum. The two square return tubes are both arranged on the inner wall of the drum. The inlets of the two square return tubes are both located at the starting point of the material distribution slope, and the outlets of the two square return tubes are both located in the material guide area; the two square return tubes extend in a spiral shape, and the two square return tubes are arranged axially symmetrically with the center line of the drum.

8. The S-NPK production system according to claim 4, characterized in that: The angle between the axis of the drum and the horizontal direction is α, 4°≥α≥0.5°; the feed inclined plate forms an angle of 10°~15° with the center line of the drum, and each shoveling plate is parallel to the axis of the drum; the material distribution slope is located at the end of the non-shoveling plate area, and the angle between the material distribution slope and the inner wall of the drum is β, 40°≥β≥30°, and the maximum height of the material distribution slope in the radial direction of the drum is Hx; the rotary screen is located at the very end of the drum and connected to the material distribution slope, and the mesh size of the rotary screen is 40×40mm; the material baffle is located in the middle of the drum, and its height in the radial direction of the drum is Hd, Hd>Hx; the distance between the axis of the material inlet and the material outlet of the granulating dryer is L, the drum diameter is D, L:D=3~4, and the drum speed is 3~6r / min.

9. A method for producing S-NPK, which is carried out using the S-NPK production system according to any one of claims 1 to 7, characterized in that: It includes the following steps: (1) Raw material feeding and S-NPK preparation section: potassium bisulfate and phosphoric acid from the boundary area are fed into the mixed acid tank, the potassium bisulfate contains KHSO4 with a mass concentration of 80% to 90%, and the phosphoric acid contains P2O5 with a mass concentration of 20% to 35%. The potassium bisulfate and phosphoric acid are fully stirred and mixed by the mixed acid agitator in the mixed acid tank to prepare mixed acid. Ammonia from the boundary area and the mixed acid prepared in the mixed acid tank are fed into a tubular reactor, and ammonia reacts with the mixed acid in the tubular reactor to form S-NPK slurry. The S-NPK slurry is prepared by mixing the potassium bisulfate and phosphoric acid in the mixed acid agitator in the mixed acid tank. The molar ratio of ammonia to phosphoric acid in the NPK slurry is NH3:H3PO4=10~13:

10. The S-NPK slurry after the reaction in the tubular reactor and the ammonia from the boundary zone are introduced into the neutralization tank. In the neutralization tank, the ammonia and the S-NPK slurry react to continue to generate S-NPK slurry. The molar ratio of ammonia to phosphoric acid in the slurry is NH3:H3PO4=14~17:10, and the mass percentage of H2O is 25~35%. The S-NPK slurry after the reaction in the neutralization tank is introduced into the slurry spray gun; (2) S-NPK spray granulation drying section: The S-NPK slurry from the neutralization tank enters the central tube of the slurry spray gun, and the compressed air from the boundary area enters between the outer tube and the central tube of the slurry spray gun. Under the action of the compressed air, the S-NPK slurry is atomized and sprayed into the granulation dryer. After atomization, the S-NPK slurry forms granular materials under the action of the granulation dryer. The granular materials are discharged from the material outlet of the granulation dryer and enter the grading screen; (3) S-NPK screening and discharging section: The granular S-NPK material from the granulation dryer is classified on the grading screen. The S-NPK coarse particles with a particle size greater than 4 mm are discharged from the grading screen through the coarse particle outlet and then enter the crusher for crushing. The crushed material is returned to the granulation dryer as external return material; the S-NPK fine particles with a particle size less than 2 mm are discharged from the grading screen through the fine particle outlet and then returned to the granulation dryer as external return material; the qualified S-NPK particles with a particle size of 2-4 mm are discharged from the grading screen through the qualified particle outlet as the target product - S-NPK.

10. The method for producing S-NPK according to claim 9, wherein: The S-NPK spray granulation drying process of step (2) is as follows: the S-NPK slurry is atomized by a spray gun and sprayed on the material curtain lifted by the shoveling plate, and dried with hot air at 250℃~320℃; as the granulation dryer drum rotates, the external return material from the material inlet and the internal return material from the square return pipe are all added to the material guide area, and the return material is introduced into the granulation area by the feed inclined plate to provide S-NPK solid particles for the material curtain. The S-NPK solid particles are repeatedly coated, granulated and dried and move from the granulation area to the drying area and the non-shoveling plate area. In the non-shoveling plate area, large particles cross the material separation slope and enter the screening area, and fine particles are deposited on the material separation slope. The large particles entering the screening area are screened by a drum screen, and the oversized particles with a particle size greater than 40 mm are left in the screening area and picked out regularly. The large particles S-NPK with a particle size less than 40 mm are discharged from the granulation dryer from the material outlet as the discharge material. The discharged S-NPK particles contain 1% to 2% by mass of H2O; the ratio of internal return material to discharge material is 2 to 4:1; the ratio of external return material to target product is 5 to 15:10; the target product contains 1% to 2% by mass of water, and the molar ratio of ammonia to phosphoric acid is NH3:H3PO4=14 to 17:10.

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