Ammonia-acid method compound fertilizer production system and process

Abstract

The invention relates to the technical field of compound fertilizer production, and discloses an ammonia-acid method compound fertilizer production system and process, the ammonia-acid method compound fertilizer production system comprises a raw material preparation unit, a reaction unit, a granulation unit and a drying unit which are communicated through pipelines, and the granulation unit comprises a dissolving tank, a primary mixing tank, a secondary mixing tank and a rotary drum granulator which are communicated; the reaction unit comprises an ammonium phosphate dissolving tank and a tubular reactor, the tubular reactor is provided with a plurality of inlets, and an outlet of the ammonium phosphate dissolving tank is communicated with one inlet of the tubular reactor; the raw material preparation unit is communicated with the ammonium phosphate dissolving tank, the dissolving tank, the primary mixing tank and other inlets of the tubular reactor; an outlet of the tubular reactor is communicated with the rotary drum granulator, and an outlet of the rotary drum granulator is communicated with the drying unit. According to the scheme, different types of raw materials are subjected to reaction treatment and then are sufficiently mixed in a liquid state for granulation, so that the mixing uniformity of various materials is effectively improved, and the stability of compound fertilizer granules obtained by granulation is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of compound fertilizer production, and particularly relates to an ammonium-acid method compound fertilizer production system and process. Background Art

[0002] Ammonium-acid method compound fertilizer is produced by neutralizing sulfuric acid, phosphoric acid with ammonia to generate compound fertilizers containing various nutrients. It can effectively improve the utilization rate of elements such as nitrogen and phosphorus in fertilizers, and has advantages such as balanced nutrients and quick fertilizer effect, and is widely used in agricultural production.

[0003] There have been various publicly reported production processes for existing ammonium-acid method compound fertilizers: Patent CN104987158A discloses an ammonium-acid method compound fertilizer production process. First, dilute sulfuric acid and ammonia water are put into a tubular reactor for reaction to generate ammonium sulfate slurry with high temperature, high pressure and high steam. Then, the ammonium sulfate slurry is sprayed into a rotary drum granulator with pre-laid materials (alternately laid and mixed with urine obtained by melting potassium chloride and monoammonium phosphate after being respectively crushed). Granulation is completed, and then through processes such as drying and screening, the finished product is obtained. Patent CN102336599A discloses a process for producing high-concentration compound fertilizers by the ammonium-acid method. After dilute phosphoric acid, dilute sulfuric acid and ammonia complete the reaction in a tubular reactor, they are pumped into a granulator and granulated together with urea and ammonium chloride fed into the granulator to obtain compound fertilizers. Its purpose is to replace part of monoammonium phosphate with dilute phosphoric acid ammoniation and ammonium chloride. And in order to ensure that the content of free phosphoric acid in the compound fertilizer product is qualified, it is required that the ammonia fed into the tubular reactor should make the dilute phosphoric acid react completely, that is, there should be no residual phosphoric acid in the reaction product. However, the above existing technologies still have the following technical problems:

[0004] (1) In the existing production process CN104987158A, granulation depends on the heat release and humidity of the neutralization reaction of dilute sulfuric acid and ammonia water. During the process of mixing and granulating with other solid raw materials laid in the granulator, it is easy to have uneven mixing or uneven coating of raw materials, resulting in unstable quality of the compound fertilizer obtained by granulation and reducing the product quality.

[0005] (2) In the existing production process CN104987158A, during the mixing process of ammonium sulfate slurry with high temperature, high pressure and high steam and the laid raw materials, the granulation pressure and strength of each part of the raw materials are uneven, resulting in low or uneven compressive strength of the compound fertilizer particles obtained by production, and being easy to break during storage and transportation, thus reducing the product quality.

[0006] (3) In the existing production process CN102336599A, phosphoric acid and ammonia gas are used to neutralize the reaction to produce monoammonium phosphate, and the method of adding ammonium chloride is used to replace part of monoammonium phosphate. It not only requires that the ammonia fed into the tubular reactor should make the dilute phosphoric acid react completely, increasing the difficulty of implementation, but also there is still a problem of uneven mixing during the subsequent granulation process, resulting in unstable quality of the compound fertilizer.

[0007] In view of this, developing a production system and process for amino acid compound fertilizers with evenly mixed raw materials not only effectively makes up for the deficiencies of the existing technology, but also can effectively improve the stability and uniformity of the compound fertilizers obtained in production, which is of great significance for improving product quality and facilitating transportation. Summary of the Invention

[0008] The present invention aims to provide a production system and process for amino acid compound fertilizers to solve the technical problem that when producing compound fertilizers by the amino acid method, the raw materials are prone to uneven mixing, which reduces the stability of the compound fertilizers.

[0009] To achieve the above object, the present invention adopts the following technical scheme: The amino acid compound fertilizer production system includes a raw material preparation unit, a reaction unit, a granulation unit, and a drying unit connected by pipelines. The granulation unit includes a dissolution tank, a primary mixing tank, a secondary mixing tank, and a drum granulator connected in sequence; the reaction unit includes a phosphoric acid ammonium dissolution tank and a tubular reactor. The tubular reactor is provided with multiple inlets, and the outlet of the phosphoric acid ammonium dissolution tank is connected to one inlet of the tubular reactor; the raw material preparation unit is connected to the phosphoric acid ammonium dissolution tank, the dissolution tank, the primary mixing tank, and the other inlets of the tubular reactor; the outlet of the tubular reactor is connected to the secondary mixing tank, and the outlet of the granulator is connected to the drying unit.

[0010] The principle and advantages of this solution are as follows:

[0011] 1. Compared with the existing method of directly laying raw materials in the granulator and mixing them with the slurry obtained by amino acid neutralization, which is prone to uneven mixing and reduces the product stability, in this solution, different types of raw materials are subjected to reaction treatment or primary dissolution and mixing, and then fully mixed in a liquid state for granulation, effectively improving the mixing uniformity of various materials, and thus improving the stability of the compound fertilizer particles obtained by granulation.

[0012] 2. Compared with the existing technology that requires strict control of the ammonia gas addition amount in the tubular reactor to ensure complete reaction of phosphoric acid, which has strict control requirements, in this solution, monoammonium phosphate is liquefied in advance in the phosphoric acid ammonium dissolution tank, not only effectively improving the mixing and reaction effect of monoammonium phosphate, sulfuric acid, and ammonia gas. In addition, the unreacted raw materials in the tubular reactor can be further fully mixed and reacted in the secondary mixing tank and the drum granulator (both the mixing and reaction of monoammonium phosphate, sulfuric acid, and ammonia gas, and the reaction of these three with other raw materials such as urea), thus effectively ensuring that there is no excessive free acid residue in the raw materials, reducing the feed control requirements on the basis of ensuring the nutrition and quality of the final product, and improving the production success rate.

[0013] 3. Compared with the prior art where other additives (such as potassium salts, urea, fillers, etc.) are alternately laid in the granulator and are prone to uneven mixing, in this solution, different additives are respectively processed in the dissolution tank and the primary mixing tank according to their respective properties and then mixed, effectively ensuring the full mixing of various additives, thus ensuring their full mixing with the sulfuric acid slurry obtained from the amino acid neutralization reaction, further improving the mixing uniformity of the granulation materials, ensuring the balanced compressive properties of the particles obtained from the granulation materials, and improving the product quality.

[0014] Preferably, as an improvement, the raw material preparation unit includes a urea bin, a potassium salt bin, an ammonium salt bin, a filler bin, a monoammonium phosphate bin, a sulfuric acid tank, and an ammonia gas tank. The monoammonium phosphate bin is connected to the monoammonium phosphate dissolution tank; the sulfuric acid tank and the ammonia gas tank are connected to the inlet of the tubular reactor; the urea bin is connected to the dissolution tank, and the potassium salt bin, the ammonium salt bin, and the filler bin are all connected to the primary mixing tank.

[0015] Technical effect: With the above settings in this solution, it is convenient for the raw materials to be separately fed for reaction, mixed, and then granulated to form compound fertilizer particles.

[0016] Preferably, as an improvement, it further includes a screening unit, a cooling unit, a coating unit, a finished product packaging unit, and a tail gas treatment unit. The tail gas treatment unit is connected to the raw material preparation unit, the reaction unit, the granulation unit, the drying unit, the screening unit, the cooling unit, and the coating unit.

[0017] Technical effect: With the above settings in this solution, the waste gases generated in each stage of compound fertilizer production are effectively collected, avoiding environmental pollution and effectively improving the environmental benefits. Compared with the prior art where tail gas treatment is often ignored or the treatment is single, in this solution, the tail gas treatment unit collects the waste gases from each link and centrally treats them, improving the environmental protection benefits and resource utilization rate, realizing the overall optimization of the production system, and effectively making up for the deficiencies of the prior art.

[0018] Preferably, as an improvement, the screening unit and the cooling unit include a fine screening device, a first cooling device, a fine screening device, and a second cooling device that are sequentially connected. The tail gas outlets of the fine screening device, the fine screening device, and the second cooling device are connected to the air inlet pipe of the first cooling device.

[0019] Technical effect: By setting the tail gas outlets of the fine screening device, the fine screening device, the second cooling device, and the coating unit to be connected to the refrigerant inlet of the first cooling device, this solution not only realizes the recycling of the waste heat of the tail gas and reduces the amount of tail gas, but also effectively recovers and utilizes the trace powders in the tail gases of the fine screening device, the fine screening device, the second cooling device, and the coating unit, avoiding their direct discharge into the tail gas treatment unit and waste.

[0020] Preferably, as an improvement, the cooling unit, the screening unit and the coating unit are arranged in a three-story building; the discharge end of the fine screening device arranged on the second floor is communicated with the feed end of the first cooling device arranged on the first floor, and the first cooling device and the fine screening device arranged on the third floor are communicated through an elevator; the discharge end of the fine screening device is communicated with the vertically arranged second cooling device, the second cooling device straddles the second floor and the first floor, the discharge end of the second cooling device is communicated with a belt conveyor, and the discharge end of the belt conveyor is communicated with the coating machine arranged on the third floor through an elevator, and the discharge end of the coating machine is provided with a discharge main pipe.

[0021] Technical effect: With the above arrangement in this solution, it is convenient to ensure the effective and smooth connection of materials, improve the space utilization rate and facilitate maintenance. Moreover, it effectively reduces the number of elevators, reduces the equipment cost and space cost, simplifies the conveying process, reduces the complexity of collaborative operation, and is beneficial to improving the conveying efficiency and production efficiency.

[0022] Preferably, as an improvement, the drying unit includes two-stage drying devices arranged continuously, and each drying device includes a cylinder body, a feed hopper, a heating device, an air guiding device and an anti-adhesion feeding assembly; the feed hopper, the heating device and the anti-adhesion feeding assembly are all located at the feed end of the cylinder body, and the air guiding device is located at the discharge end of the cylinder body; the anti-adhesion feeding assembly includes an inclined chute and a heat insulation chute, the inclined chute communicates the feed hopper and the inside of the cylinder body, and the heat insulation chute is located between the inclined chute and the heating device, and the heat insulation chute communicates the inside and the outside of the cylinder body.

[0023] Technical effect: With the above arrangement in this solution, it is convenient to dry the compound fertilizer particles while preventing too many particles from adhering to the inclined chute and affecting. Specifically, during the drying process, the air guiding device continuously draws air, making the inside of the cylinder body in a slightly negative pressure state, attracting external air to continuously enter the cylinder body from the heat insulation chute, and maintaining the normal temperature (low temperature) of the heat insulation chute. The heating device introduces hot air into the cylinder body. After the hot air enters the cylinder body, it first contacts the normal-temperature heat insulation chute, and then mixes with the air in the cylinder body to dry the materials entering the cylinder body from the inclined chute. Due to the blocking of the heat insulation chute, the hot air is effectively prevented from directly heating the inclined chute, thus effectively preventing the inclined chute from having too high a temperature and dissolving the materials to cause stacking or blockage, ensuring the smooth feeding of the inclined chute, facilitating continuous production and improving production efficiency, and also prolonging the service life of the inclined chute and the equipment. Moreover, while the heat insulation chute protects the inclined chute, it also prevents the product particles from being dissolved and damaged, thereby improving the stability of the product.

[0024] Compared with the existing drum dryers, when hot air is blown into the cylinder, it is easy to dissolve and adhere the materials at the feeding chute, resulting in channel blockage, particle breakage and chute damage. In the drying device of this solution, the heat insulation groove is located between the chute and the heating device, and the heat insulation groove communicates with the inside and outside of the cylinder, effectively preventing the hot air introduced by the heating device from directly heating the chute and causing the materials to dissolve and adhere in the chute, maintaining smooth feeding, avoiding production shutdown and maintenance due to material blockage and equipment failure, and effectively improving production continuity and production efficiency. Moreover, this solution avoids the dissolution and adhesion of materials in the feeding stage, reduces the damage of the particle material structure, effectively improves the quality stability of the particle products, improves the overall quality of the products, and improves the economic benefits.

[0025] Preferably, as an improvement, the lowest end of the heat insulation groove is higher than the lowest end of the chute, and a mixing area is formed between the lower part of the lowest end of the heat insulation groove and the lower end of the bottom wall of the chute.

[0026] Technical effect: With the above settings in this solution, the hot air is mixed with the air inside the cylinder (including the external cold air inhaled from the heat insulation groove) under the guidance of the heat insulation groove and is reduced to a suitable temperature, effectively improving the drying effect. Specifically, the above settings enable the hot air to be mixed with the external cold air inhaled from the heat insulation groove in the mixing area first and then contact the materials, effectively preventing the cold air from directly contacting the materials and reducing the drying effect of the materials. The applicant found through long-term experiments that if the lowest end of the heat insulation groove is lower than the lowest end of the chute, not only will the cold air reduce the drying effect, but also the hot air will not be cooled by the cold air before contacting the materials, and its temperature is still relatively high, resulting in the hot air still dissolving some materials when directly contacting the materials at the lowest end of the chute and adhering to the lowest end of the chute, still causing material adhesion at the bottom end of the chute, thus affecting the operation effect of the equipment and reducing the quality stability of the products.

[0027] Preferably, as an improvement, this solution also provides a production process for amino acid compound fertilizer, which is completed based on the above amino acid compound fertilizer production system, and includes the following steps:

[0028] Step 1, amino acid neutralization reaction stage: Ammonia gas, sulfuric acid and ammonium phosphate slurry are mixed and reacted to obtain sulfuric acid slurry;

[0029] Step 2, additive preparation stage;

[0030] Step 3, granulation stage: The above sulfuric acid slurry and additives are mixed evenly in a rotary drum granulator and granulated to obtain compound fertilizer particles;

[0031] Step 4, post-treatment stage: The compound fertilizer particles are successively subjected to drying treatment, screening treatment, cooling treatment, coating treatment and finished product packaging treatment to obtain compound fertilizer particle products.

[0032] Technical effect: With the above settings in this solution, part of the raw materials are first produced into a sulfuric acid slurry containing monoammonium phosphate, and then mixed and granulated with other additives, which is convenient for producing compound fertilizer granules with uniform distribution of nutrient elements, thereby effectively improving the quality of compound fertilizer products.

[0033] Preferably, as an improvement, in step one, the ammonium phosphate slurry is obtained by heating and dissolving with water at 70 - 90 °C.

[0034] Technical effect: With the above settings in this solution, it is convenient to form an ammonium phosphate slurry with better fluidity (semi-dissolved state is also acceptable) from monoammonium phosphate, which is convenient for its full reaction with sulfuric acid and gaseous ammonia to obtain a sulfuric acid slurry under high temperature and high pressure; after the sulfuric acid slurry is mixed with other additives, the mixing uniformity effect of the mixed materials is further improved, thereby improving the stability of compound fertilizer granules.

[0035] Preferably, as an improvement, the additives include potassium salts, ammonium salts, urea, and fillers, and the fillers are one or a combination of bentonite, white clay, diatomite, vermiculite, and ceramic slag.

[0036] Technical effect: With the above settings in this solution, it is convenient to produce compound fertilizer granules that meet the nutrient requirements for crop growth. Specifically, during the sowing period and seedling stage, 10 - 20 - 10 to 15 - 15 - 15 (referring to the N - P 2 O 5 -K 2 O content, the same below) promotes root development and enhances stress resistance; during the vegetative growth period, 20 - 10 - 10 to 25 - 5 - 15 is required to support the rapid growth of leaves and stems and increase photosynthesis; during the flowering period, 10 - 20 - 20 to 15 - 15 - 30 is required to promote flower bud differentiation and flower formation and improve the pollination rate; during the fruiting period, 10 - 10 - 30 to 15 - 15 - 25 is required to promote fruit swelling and sugar accumulation and improve fruit quality; after harvest and during the recovery period, 15 - 15 - 15 to 20 - 20 - 20 is required to promote root repair and leaf recovery and enhance stress resistance, etc.

[0037] Preferably, the drying treatment includes primary drying and secondary drying carried out continuously. The temperature of the primary drying is 150 - 300 °C and the drying time is 15 - 20 min, and the temperature of the secondary drying is 80 - 200 °C and the drying time is 10 - 15 min; the screening treatment and cooling treatment include fine screening, primary cooling, fine screening, and secondary cooling carried out in sequence.

[0038] Technical effect: With the above settings in this solution, it is convenient to quickly dry, screen, and cool to obtain compound fertilizers that meet product requirements. Specifically, the temperature and time of the first drying are mainly to quickly remove the free moisture on the surface of the compound fertilizer particles, while not decomposing the nutrients in the fertilizer or causing other adverse chemical reactions. After the first drying, most of the moisture inside the compound fertilizer particles has been transferred to the surface. The second drying effectively further removes the remaining moisture and simultaneously performs the final drying and shaping of the fertilizer particles. Through long-term experiments, the applicant found that if the number of drying times is too small, it is easy for the product to be affected by moisture and caking due to the ineffective removal of the moisture inside the compound fertilizer particles, which affects the product quality and storage performance; if the drying temperature is too high, it will cause the decomposition of the fertilizer components or the generation of harmful by-products (such as the formation of biuret from urea), and cracks will appear due to excessive drying on the surface of the particles, affecting the strength and appearance of the particles and resulting in nutrient loss of the fertilizer and a decline in product quality; if the drying temperature is too low, it will cause the product to have too high a water content due to the ineffective removal of moisture, not meeting the product standards. If only one screening is carried out, the product particle size will be uneven and the impurity content will be high because the qualified products and impurities in different particle size ranges cannot be effectively separated; if only one cooling is carried out, the product temperature will be too high due to insufficient cooling, and water vapor may be generated inside the packaging bag during subsequent packaging and other processes, affecting the product quality. If screening is carried out completely first and then cooling, the local temperature of the product will be too high due to the heat accumulation generated during the screening process not being dissipated in time, which may affect the product quality and stability.

[0039] Preferably, as an improvement, in step one, the mixing ratio of gaseous ammonia, sulfuric acid, and ammonium phosphate slurry is 1.8 - 2.2: 0.9 - 1.1: 1.8 - 2.2.

[0040] Technical effect: With the above settings in this solution, it is convenient for the three to be fully mixed and reacted, and the remaining raw materials are reduced as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic structural diagram of the amino acid method compound fertilizer production system in the embodiment of the present invention.

[0042] Figure 2 It is a material flow diagram of the amino acid method compound fertilizer production process in the embodiment of the present invention.

[0043] Figure 3 It is a schematic structural diagram of the existing drying equipment.

[0044] Figure 4 It is a partial structural diagram of the drying device in the embodiment of the present invention.

[0045] Figure 5 It is a top view of the heat insulation tank and the inlet of the inclined trough in the embodiment of the present invention.

[0046] Figure 6 This is the left view of the heat insulation groove and the inclined groove in the embodiment of the present invention.

[0047] Figure 7 This is a schematic structural diagram of another possible positional relationship between the heat insulation groove and the inclined groove in the embodiment of the present invention.

[0048] Figure 8 This is a schematic structural diagram of the post-treatment three-dimensional subsystem of compound fertilizer in the embodiment of the present invention. Detailed implementation manners

[0049] The present invention will be further described in detail below with reference to embodiments, but the implementation manners of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial channels.

[0050] The markings in the accompanying drawings of the specification include: heating device 201, dust collector 202, induced draft fan 203, cylinder body 21, discharge port 211, feed hopper 22, inclined groove 23, heat insulation groove 24, mixing area 25, first floor 301, second floor 302, third floor 303, fine screening device 311, precision screening device 312, powder material discharge pipe 313, coarse material discharge pipe 314, first cooling device 321, second cooling device 322, belt conveyor 33, film coating machine 34, total discharge pipe 341, return material scraper 35, dust suction hood 361, dust collection main pipe 362, tail gas pipe 363.

[0051] General description of the solution

[0052] This solution provides a production system for amino acid compound fertilizer, basically as Figures 1 to 8 shown: It includes a raw material preparation unit, a reaction unit, a granulation unit, a drying unit, a screening unit, a cooling unit, a film coating unit, a finished product packaging unit and a tail gas treatment unit connected by pipelines.

[0053] As an improvement, the raw material preparation unit includes several bins / tanks, including a urea bin, a potassium salt bin, an ammonium salt bin, a filler bin, a monoammonium phosphate bin, a sulfuric acid tank, and an ammonia gas tank.

[0054] As an improvement, the reaction unit includes a monoammonium phosphate dissolution tank and a tubular reactor. The monoammonium phosphate bin is connected to the monoammonium phosphate dissolution tank; the tubular reactor is provided with multiple inlets, and the outlet of the monoammonium phosphate dissolution tank is connected to one inlet of the tubular reactor; the other inlets of the tubular reactor are respectively connected to the sulfuric acid tank and the ammonia gas tank, facilitating the introduction of sulfuric acid and ammonia gas into the tubular reactor.

[0055] The granulation unit includes a dissolution tank, a first-stage mixing tank, a second-stage mixing tank, and a drum granulator that are connected in sequence. The urea storage bin is connected to the dissolution tank and is used to dissolve urea. The potassium salt storage bin, the ammonium salt storage bin, and the filler storage bin are all connected to the first-stage mixing tank. The outlet of the tubular reactor is connected to the second-stage mixing tank, and the outlet of the drum granulator is connected to the drying unit.

[0056] As an improvement, the drying unit includes two-stage drying devices arranged continuously, as Figure 4 shown. The drying device includes a cylinder body 21, a feed hopper 22, a heating device, an air extraction device, and an anti-adhesion feeding assembly; the feed hopper 22, the heating device, and the anti-adhesion feeding assembly are all located at the feed end of the cylinder body 21, and the air extraction device is located at the discharge end of the cylinder body 21. The anti-adhesion feeding assembly includes an inclined chute 23 and a heat insulation chute 24. The inclined chute 23 communicates the feed hopper 22 with the inside of the cylinder body 21, and the heat insulation chute 24 is located between the inclined chute 23 and the heating device. The heat insulation chute 24 communicates the inside and the outside of the cylinder body. As an improvement, the lowest end of the heat insulation chute 24 is higher than the lowest end of the inclined chute 23, and a mixing area 25 is formed between the lowest end of the heat insulation chute 24 and the lower end of the bottom wall of the inclined chute 23.

[0057] Specifically, as Figure 5 and Figure 6 shown, in this embodiment, the width of the heat insulation chute 24 is greater than or equal to the width of the bottom wall of the inclined chute 23. The heat insulation chute 24 is welded to the bottom wall of the inclined chute 23 and forms a heat insulation channel with the bottom wall of the inclined chute 23. The inlet of the heat insulation channel communicates with the outside, and the outlet is located inside the cylinder body 21. As a reference, in this embodiment, the heat insulation chute 24 is in a semi-circular arc structure, which is beneficial to guiding the hot air, so that the hot air can be better introduced into the cylinder body 21 and mixed with the cold air in the mixing area 25 for drying the granular material.

[0058] In another embodiment of this solution, as Figure 7 shown, the upper ends of the heat insulation chute 24 and the inclined chute 23 are welded, and the lower ends are separated (for example, the inclination angle of the inclined chute 23 can be 45°, and the inclination angle of the heat insulation chute 24 can be 60°). At this time, the range of the mixing area 25 is larger, which is more conducive to the mixing of cold and hot air and further improves the drying effect of the granular material.

[0059] Existing drying equipment such as Figure 3As shown, during the feeding process of compound fertilizer, it is not only easily melted by hot air and adhered to the chute 23, but also during the actual production, in the drying process after compound fertilizer granulation, due to the increase in temperature and evaporation of moisture, the compound fertilizer particles may agglomerate to a certain extent, especially in an environment with higher humidity. These agglomerations will affect the uniformity and fluidity of the product and reduce the product quality. However, in this solution, by setting the heat insulation groove 24 and the mixing zone 25 in the drying device, it not only effectively avoids the dissolution and adhesion of compound fertilizer particles on the chute 23, but also can be mixed with hot air at an appropriate temperature to achieve the "slow" drying of compound fertilizer particles, effectively reducing the rapid increase in particle temperature and rapid evaporation of moisture caused by the direct contact of hot air with the particles, effectively improving the drying effect of compound fertilizer particles, and thus improving the product quality.

[0060] Among them, the two-stage drying device is specifically a connected first-stage drying device and a second-stage drying device. When producing urea formaldehyde sulfate compound fertilizer using the ammonium acid method compound fertilizer production system of this solution, it also includes a urea formaldehyde reaction tank and an intermediate tank. The feeding end of the urea formaldehyde reaction tank is connected to the formaldehyde tank, the urea bin, and the caustic soda bin. The discharging end of the intermediate tank is connected to the second-stage drying device to convey the urea formaldehyde solution to the second-stage dryer, which is convenient for spraying and coating when the compound fertilizer has a certain strength and low water content. While effectively obtaining urea formaldehyde sulfate compound fertilizer, it can avoid the crushing or material detachment of the compound fertilizer when impacted by the spraying of the urea formaldehyde solution, thus effectively ensuring the uniformity of the compound fertilizer particle size and further improving the compound fertilizer production efficiency.

[0061] As an improvement, the screening unit and the cooling unit include a fine screening device, a first cooling device, a fine screening device, and a second cooling device that are connected in sequence. The first cooling device has the same structure as the aforementioned drying device, which is convenient for better screening and cooling of the dried granular material. The coating unit includes a coating machine, and the finished product packaging unit includes a packaging machine.

[0062] As an improvement, the tail gas treatment unit is connected to the raw material preparation unit, the reaction unit, the granulation unit, the drying unit, the screening unit, the cooling unit, and the coating unit. Specifically, the tail gases of the drum granulator, the first-stage drying device, the second-stage drying device, the fine screening device, the first cooling device, the fine screening device, the second cooling device, and the coating machine are collected and transported to the tail gas treatment unit for centralized treatment. Only the tail gas outlets of the fine screening device, the fine screening device, the second cooling device, and the coating machine are connected to the air inlet pipe of the first cooling device, and after being used as a refrigerant to cool the material in the first cooling device, they are uniformly discharged to the tail gas treatment unit for treatment.

[0063] As an improvement, when installing the equipment of the screening unit, the cooling unit, and the coating unit in a specific workshop, in order to improve the space utilization rate and facilitate maintenance, this solution also provides a three-dimensional subsystem for compound fertilizer post-treatment, such as Figure 8As shown in the figure, it includes a cooling unit, a screening unit, and a coating unit distributed on three floors. Specifically, the discharge end of the fine screening device 311 installed on the second floor 302 is connected to the feed end of the first cooling device 321 installed on the first floor 301. The first cooling device 321 and the fine screening device 312 installed on the third floor 303 are connected through an elevator. The discharge end of the fine screening device 312 is connected to a vertically arranged second cooling device 322. The second cooling device 322 straddles the second floor 302 and the first floor 301. The discharge end of the second cooling device 322 is connected to a belt conveyor 33. The discharge end of the belt conveyor 33 is connected to a coating machine 34 installed on the third floor 303 through an elevator. The discharge end of the coating machine 34 is provided with a discharge main pipe 341.

[0064] As a reference, both the fine screening device 311 and the fine screening device 312 can be grading screens; the structure of the first cooling device 321 is the same as that of the aforementioned drying device, and only the heating device connected to the cylinder body 21 needs to be replaced with a refrigerant supply device; the second cooling device 322 can be a plate cooler.

[0065] In other embodiments of this solution, according to production needs, the fine screening device 312 and the coating machine 34 installed on the third floor 303 can also be installed on the fourth floor and above, or an installation platform can be directly built in the upper part of the space on the second floor 302, and the fine screening device 312 can be installed on the installation platform; the lower space on the second floor 302 can also be used to observe and maintain the equipment on the second floor 302. In this embodiment, by installing the fine screening device 312 on the third floor 303, the spatial position of the fine screening device 312 is raised compared to before the improvement, so that the discharge port of the fine screening device 312 can be directly aligned with the feed end of the second cooling device 322 in space, facilitating the screened material to directly enter the second cooling device 322, thus achieving effective connection of the material, eliminating the need to set an elevator between the fine screening device 312 and the second cooling device 322, reducing the number of elevators, lowering the equipment cost and space cost, simplifying the conveying process, reducing the complexity of collaborative operations, and being conducive to improving the conveying efficiency and production efficiency.

[0066] In addition, powder discharge pipes 313 and coarse material discharge pipes 314 are provided at the bottoms of both the fine screening device 311 and the fine screening device 312. The discharge ends of the powder discharge pipes 313 and the coarse material discharge pipes 314 are connected to a return scraper conveyor 35, facilitating the recovery of compound fertilizer particles with too large or too small particle sizes, and waiting to be recycled to prepare compound fertilizer particles after reprocessing.

[0067] As an improvement, dust suction hoods 361 are provided at the tops of the fine screening device 311, the fine screening device 312, the coating machine 34, and the return crusher. The dust suction hoods 361 are connected to the air inlet pipe of the first cooling device 321 through a dust removal main pipe 362. The top of the first cooling device 321 is connected to an exhaust pipe 363. One end of the exhaust pipe 363 is connected to a dust collector (as a reference, such as Figure 1As shown, it can be a cyclone dust collector and a bag filter connected in sequence). That is, in this solution, the tail gas in the fine screening device 311, the fine screening device 312 and the film coating machine 34 is used as a refrigerant to supply the primary cooling device 321 to cool the material, and finally discharged uniformly from the tail gas pipe 363. On the one hand, the tail gas of some devices is effectively recycled, reducing the total tail gas volume in the post-treatment stage and the energy consumption of tail gas treatment; on the other hand, during the countercurrent cooling of the recycled tail gas and the material in the primary cooling device 321, dust adheres to the particles, and part of the dust in the tail gas can also be recovered, further reducing the energy consumption of dust treatment.

[0068] This solution also provides an ammonium acid compound fertilizer production process, which is completed based on the above ammonium acid compound fertilizer production system, and includes the following steps:

[0069] Step 1. Sulfuric acid slurry preparation stage: Monoammonium phosphate is first heated and dissolved in water at 70-90 °C to obtain ammonium phosphate slurry. Subsequently, sulfuric acid, gaseous ammonia and ammonium phosphate slurry are mixed and reacted to obtain sulfuric acid slurry containing monoammonium phosphate; the mixing ratio of gaseous ammonia, sulfuric acid and ammonium phosphate slurry is 1.8-2.2: 0.9-1.1: 1.8-2.2.

[0070] In addition, the unreacted sulfuric acid in the tubular reactor and the gaseous ammonia in the granulator will continue to react and release heat, which cooperates with steam to heat the material, effectively providing a stable reaction environment and temperature conditions for the granulation process.

[0071] Step 2. Additive preparation stage; including preparing potassium salt, ammonium salt, urea and white mud (mainly composed of kaolin).

[0072] Step 3. Granulation stage: The above sulfuric acid slurry and additives are mixed evenly and granulated to obtain compound fertilizer particles;

[0073] Specifically, urea is dissolved in a dissolution tank in advance to form a urea solution. Subsequently, the urea solution is mixed with additives such as potassium chloride, ammonium sulfate and white mud in a primary mixing tank, and the mixed material then enters a secondary mixing tank to be mixed evenly with the sulfuric acid slurry and then enters a rotary drum granulator to obtain compound fertilizer particles through granulation;

[0074] Step 4. Post-treatment stage: The compound fertilizer particles are successively subjected to drying treatment, screening treatment, cooling treatment, film coating treatment and finished product packaging treatment to obtain compound fertilizer particle products. Among them, the drying treatment includes continuous first drying and second drying. The temperature of the first drying is 150-300 °C and the drying time is 15-20 min. The temperature of the second drying is 80-200 °C and the drying time is 10-15 min; the screening treatment and the cooling treatment include sequential fine screening, primary cooling, fine screening and secondary cooling.

[0075] As a reference, the hot air of a drying device comes from a hot blast stove fueled by natural gas, and the air required for combustion to adjust the furnace gas temperature is provided by a bottom blower of the furnace. The hot air from the hot blast stove and the materials conveyed by the belt of the granulator enter the first drying device together. After being dried in the first drying process, they are then conveyed by an elevator to the second drying device. After the second drying, the compound fertilizer particles enter the first cooling device after being preliminarily screened by a fine screening device. After preliminary cooling, they are conveyed by an elevator to the fine screening device. After being screened again, the compound fertilizer particles with appropriate particle sizes are conveyed to a plate cooler for secondary cooling. The finished products after temperature reduction are weighed and then sent to a coating machine for coating. The coated finished products are conveyed by a finished product conveying belt to a packaging workshop for packaging.

[0076] Meanwhile, during the screening process of the finished products, the large and small particles screened out are sent to the scraper conveyor for returned materials, the returned material bin, and the returned material metering belt for metering, and then fed into the scraper conveyor after being metered with potassium sulfate, and returned to the system for on-line use.

[0077] The tail gas discharged from the cooling, screening, and coating equipment (first recovered into the first cooling device as a refrigerant, and then discharged from the tail gas of the first cooling device) is dusted by a negative pressure pipeline through a cyclone dust collector and a bag dust collector, and then the tail gas is sent by a dust removal fan to the air inlet of the bottom scraper of the tower and used as the secondary air inlet of the air in the tower.

[0078] When this solution is specifically applied to the production of urea-sulfuric acid-formaldehyde compound fertilizer, it also includes obtaining a urea-formaldehyde solution in advance. The preparation method of the urea-formaldehyde solution is as follows:

[0079] Urea is dissolved in water in advance and the pH value is adjusted to 9 - 10 with caustic soda flakes. Subsequently, formaldehyde (molar ratio 1.5 - 1.8:1) is introduced into the reaction tank for mixing, and the reaction is carried out at 40 - 45 °C for 30 minutes. Then, a sample is taken to detect the urea-formaldehyde solution. After passing the detection, it is transferred to an intermediate tank for standby.

[0080] During specific production, the reaction end point of urea and formaldehyde is: monitor the change of pH value during the reaction process. When the pH value stabilizes at 3.5 - 5.5 ± 0.1 for 3 - 5 minutes, it can be used as an auxiliary judgment that the reaction is approaching the end point. At this time, the qualified standard for sampling detection is to meet the requirements in the chemical industry standard "HG / T4137 - 2010 Urea-formaldehyde Slow-release Fertilizer", that is, the urea-formaldehyde content of TN ≥ 36%, the urea-formaldehyde content of UN ≤ 5%, the urea-formaldehyde content of CWIN ≥ 14%, and the urea-formaldehyde content of HWIN ≤ 16%.

[0081] Subsequently, the urea-formaldehyde solution in the intermediate tank is sprayed onto the surface of the compound fertilizer particles during the second drying process, coating the compound fertilizer particles to form urea-sulfuric acid-formaldehyde compound fertilizer. After drying, it is screened by a fine screening device, preliminarily cooled by a first cooling device, secondarily screened by a fine screening device, and cooled again by a second cooling device in sequence, and then sent to the coating machine in the coating unit for coating treatment, and then sent to the packaging area for packaging to obtain urea-sulfuric acid-formaldehyde compound fertilizer products.

[0082] Using this solution to produce urea formaldehyde compound fertilizer from sodium amino acid compound fertilizer has the following technical advantages:

[0083] 1. Improve the comprehensive utilization rate of resources: In the raw material treatment and granulation sections, part of the monoammonium phosphate solid is dissolved and participates in the reaction, improving the resource utilization rate. At the same time, the tail gas circulating washing water is used in the extrusion granulation process, realizing the recycling of resources, reducing the dependence on fresh water resources, and lowering the production cost.

[0084] 2. Improve the stability of the production process: By precisely controlling the ratio of each raw material and reaction conditions in the amino acid method granulation, such as the ratio of gaseous ammonia to concentrated sulfuric acid and the addition amount of ammonium phosphate slurry, the stability of the granulation process is ensured. The continuous reaction of unreacted sulfuric acid in the tubular reactor with gaseous ammonia in the granulator and the steam heating of the material also provide a stable reaction environment and temperature conditions for the granulation process. During the preparation of urea formaldehyde, the feeding flow rate of formaldehyde, reaction temperature, and pH value are strictly controlled, and the quality stability of the urea formaldehyde solution is ensured by manual metering of urea and controlling the molar ratio, thus providing a stable coating component for the production of compound fertilizer.

[0085] 3. Effectively save energy and reduce emissions: The hot blast stove fueled by natural gas is used in the drying and cooling treatment section, with high combustion efficiency, reducing energy consumption. At the same time, the air is adjusted by the bottom blower of the furnace to make the furnace gas temperature more stable, improving the energy utilization efficiency. In the tail gas treatment section, a variety of efficient treatment methods are used for the tail gas in different links, such as Venturi scrubber, tail gas acid washing tower, tail gas washing tower, cyclone dust collector, gravity settling chamber, bag dust collector, etc., which not only effectively reduce the pollutant emissions in the tail gas, achieve the goal of energy conservation and emission reduction, but also reduce the impact on the environment.

[0086] 4. Improve product quality control: Through the crushing, metering, and precise treatment of raw materials, the quality and ratio accuracy of raw materials are ensured, laying a foundation for the production of high-quality compound fertilizer products. The drying and cooling treatment section undergoes multiple processes, including two-stage screening, cooler, finished product fine screening, and plate water cooler, etc., strictly controlling the particle size, temperature, and quality of the finished product, and improving the consistency and stability of the product. The coating machine performs coating treatment on the finished product, further improving the quality and appearance of the product and enhancing the market competitiveness of the product.

[0087] Specifically, the urea-sulfuric acid-formaldehyde compound fertilizer produced by this solution is comprehensive in nutrition and takes into account both quick-acting and long-acting nutrients. Specifically, the urea-sulfuric acid-formaldehyde compound fertilizer not only contains a large number of elements such as nitrogen, phosphorus, and potassium, but may also be added with a variety of medium and trace elements, which can provide comprehensive nutritional support for crop growth and meet the diverse needs of different growth stages of crops. In terms of nutrient release, the acyl nitrogen that has not formed urea-formaldehyde can be quickly converted by soil microorganisms to provide quick-acting nutrients for the seedling stage of crops; while the urea-formaldehyde component will be gradually decomposed to provide medium and long-acting nutrients, achieving a good combination of quick-acting and long-acting, and ensuring that crops have nutrient supply throughout the growth cycle. Specifically, the slow-release period of the urea-sulfuric acid-formaldehyde compound fertilizer produced by this solution can be extended to a release period of 90 days, which can release nitrogen to the soil more persistently, not only providing nutrients in the early stage of plant growth, but also meeting the growth needs of plants in the later stage.

[0088] The above are only embodiments of the present invention, and common general technical solutions and / or characteristics in the solution are not described in detail here. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. Acidic acid compound fertilizer production system, characterized by: It comprises a raw material preparation unit, a reaction unit, a granulation unit and a drying unit which are connected by pipelines, wherein the granulation unit comprises a dissolving tank, a primary mixing tank, a secondary mixing tank and a rotary drum granulator which are connected; the reaction unit comprises an ammonium phosphate dissolving tank and a tubular reactor, wherein the tubular reactor is provided with a plurality of inlets, and the outlet of the ammonium phosphate dissolving tank is connected with an inlet of the tubular reactor; the raw material preparation unit is connected with the ammonium phosphate dissolving tank, the dissolving tank, the primary mixing tank and other inlets of the tubular reactor; the outlet of the tubular reactor is connected with the secondary mixing tank, and the outlet of the rotary drum granulator is connected with the drying unit.

2. The system for producing compound fertilizer using the amino acid method according to claim 1, characterized in that: The raw material preparation unit includes a urea bin, a potassium salt bin, an ammonium salt bin, a filling bin, a monoammonium phosphate bin, a sulfuric acid tank, and a gas ammonia tank. The monoammonium phosphate bin is connected to the ammonium phosphate dissolution tank; the sulfuric acid tank and the gas ammonia tank are connected to the inlet of the tubular reactor; the urea bin is connected to the dissolution tank, and the potassium salt bin, the ammonium salt bin, and the filling bin are all connected to the primary mixing tank.

3. The ammonia-acid compound fertilizer production system according to claim 1, characterized in that: It also includes a screening unit, a cooling unit, a film coating unit, a finished product packaging unit and an exhaust gas treatment unit, and the exhaust gas treatment unit is connected with the raw material preparation unit, the reaction unit, the granulation unit, the drying unit, the screening unit, the cooling unit and the film coating unit.

4. The ammonia-acid compound fertilizer production system according to claim 3, characterized in that: The screening unit and the cooling unit include a fine screening device, a first cooling device, a fine screening device and a second cooling device which are connected in sequence, and the tail gas outlets of the fine screening device, the fine screening device and the second cooling device are connected to the air inlet pipe of the first cooling device.

5. The system for producing compound fertilizer using the amino acid method according to claim 4, characterized in that: The cooling unit, screening unit and coating unit are arranged on the third floor; the discharge end of the fine screening device arranged on the second floor is connected with the feed end of the first cooling device arranged on the first floor, and the first cooling device is connected with the fine screening device arranged on the third floor through a hoist; the discharge end of the fine screening device is connected with the vertically arranged second cooling device, and the second cooling device spans the second floor and the first floor, and the discharge end of the second cooling device is connected with a belt conveyor, and the discharge end of the belt conveyor is connected with a coating machine arranged on the third floor through a hoist, and the discharge end of the coating machine is provided with a discharge main pipe.

6. The system for producing compound fertilizer using the amino acid method according to claim 1, characterized in that: The drying unit includes a two-stage drying device arranged in series, and the drying device includes a cylinder, a feed hopper, a heating device, an air-inducing device and an anti-adhesion feeding assembly; the feed hopper, the heating device and the anti-adhesion feeding assembly are all located at the feeding end of the cylinder, and the air-inducing device is located at the discharging end of the cylinder; the anti-adhesion feeding assembly includes a chute and an insulation groove, the chute connects the feed hopper and the inside of the cylinder, the insulation groove is located between the chute and the heating device, and the insulation groove connects the inside and outside of the cylinder.

7. The system for producing compound fertilizer using the amino acid method according to claim 6, characterized in that: The lowest end of the heat-insulating groove is higher than the lowest end of the chute, and a mixing zone is formed below the lowest end of the heat-insulating groove and the lower end of the bottom wall of the chute.

8. A process for producing compound fertilizer using the amino acid method, characterized in that: The system for producing compound fertilizer using the ammonia method according to any one of claims 1 to 7 is completed, comprising the following steps: Step 1, ammonia neutralization reaction stage: gaseous ammonia, sulfuric acid and ammonium phosphate slurry are mixed and reacted to obtain sulfuric acid slurry; Step 2: Adding material preparation stage; Step 3, granulation stage: the sulfuric acid slurry and the additives are mixed evenly in a drum granulator and then granulated to obtain compound fertilizer granules; Step 4, post-processing stage: the compound fertilizer particles are sequentially dried, screened, cooled, coated and packaged to obtain compound fertilizer particle products.

9. The process for producing compound fertilizer using the amino acid method according to claim 8, characterized in that: In step one, the ammonium phosphate slurry is obtained by heating and dissolving in water at 70-90°C.

10. The process for producing compound fertilizer using the amino acid method according to claim 8, characterized in that: In step one, the mixing ratio of the gaseous ammonia, sulfuric acid and ammonium phosphate slurry is 1.8-2.2:0.9-1.1:1.8-2.2.

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