A fertilizer high-tower pulping and granulation system and method

Abstract

This invention discloses a high-tower granulation system and method for fertilizer production; comprising: a melting tank, a mixing tank, and a cooling tank; the melting tank is connected to the mixing tank, and the mixing tank is connected to the cooling tank, so that the material in the melting tank, after melting, enters the mixing tank to mix with unmelted materials to form a slurry; the slurry in the mixing tank enters the cooling tank for cooling before granulation; the melting tank is equipped with a heating device for heating and melting the material in the melting tank; the cooling tank is equipped with a cooling pipe for lowering the temperature of the material in the cooling tank; the discharge end of the cooling tank is connected to a granulation device for conveying the cooled material to the granulation device for granulation. The system and method provided by this invention, when used for high-tower granulation of fertilizer, produce granules with advantages such as being less prone to caking, having a smooth surface, and good shaping.

Description

Technical Field

[0001] This invention relates to the field of fertilizer production technology, and in particular to a fertilizer high-tower pulping and granulation system and method. Background Technology

[0002] High-tower granulation technology for fertilizers is one of the new technologies in the production process of compound fertilizers in my country. For example, in the granulation of compound fertilizers, urea or ammonium nitrate phosphate is indirectly heated and melted by steam, and then mixed with phosphate and potassium fertilizers to form a flowable slurry. This slurry is then naturally overflowed into a differential granulator and sprayed into an air-cooled tower under the action of centrifugal force. It is then cooled and crystallized into spherical particles in the counter-current airflow, thus producing compound fertilizer granules.

[0003] The production of high-tower compound fertilizer mainly includes the following processes: raw material metering and batching, pulping and granulation, air-cooled tower cooling and pelletizing, collection at the bottom of the tower, primary cooling, screening, secondary cooling, coating, packaging and stacking.

[0004] The high-tower pulping process requires a large amount of steam to indirectly heat and melt urea or ammonium nitrate phosphate. In the process of mixing in phosphate and potassium fertilizers to make a flowable slurry, steam is also required to heat the material, causing the moisture carried by the material to evaporate, reducing the moisture content of the material, and thus reducing the occurrence of product caking.

[0005] Since the process of cooling and pelletizing in an air-cooled tower is essentially fixed (the tower's height and ventilation volume cannot be changed after construction), the temperature of the slurry entering the granulator for granulation cannot be too high. Excessive temperature can lead to incomplete cooling of the granulated material, resulting in flattened solid particles that fail to meet product appearance requirements. Furthermore, excessively high slurry temperatures can cause the presence of gases (such as ammonia) generated during material decomposition. These gases can break through the slurry surface during crystallization, causing particle breakage and ultimately affecting product quality.

[0006] The temperature during the pulping process should not be too low. If the temperature is too low, it will affect the melting and mixing of the materials and will not be able to effectively evaporate the moisture in the materials to reduce the product moisture content, which will easily cause the product to clump.

[0007] Existing pulping equipment is basically composed of three or more melting (mixing) tanks, each with an internal heating coil and an external insulation pipe. Currently, the pulping equipment of high-tower compound fertilizer production enterprises is heated by steam, lacking methods for cooling materials and energy-saving devices. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, the present invention aims to provide a high-tower granulation system for fertilizers. Existing technologies lack methods for cooling materials and energy-saving devices, resulting in an irreconcilable contradiction between reducing material moisture through high temperatures and ensuring granulation quality through low temperatures during production.

[0009] The method employed in this invention involves using steam to appropriately raise the temperature of the material during the pulping process, causing the moisture in the material to evaporate. Then, low-temperature soft water is introduced through the internal heating coil and external insulation pipe of the last mixing tank before granulation (also known as the cooling tank) to cool the material, ensuring it meets the temperature requirements for granulation. Simultaneously, the hot water generated from the heat exchange between the low-temperature soft water introduced into the internal heating coil and external insulation pipe of the cooling tank and the material is returned to the boiler to recover its heat, thereby achieving energy conservation.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A fertilizer high-tower pulping and granulation system includes: a melting tank, a mixing tank, and a cooling tank; the melting tank is connected to the mixing tank, and the mixing tank is connected to the cooling tank, so that the material in the melting tank, after melting, enters the mixing tank to mix with unmelted materials to form a pulp; the pulp in the mixing tank enters the cooling tank for cooling before granulation; the melting tank is equipped with a heating device for heating and melting the material in the melting tank; the cooling tank is equipped with a cooling pipe for lowering the temperature of the material in the cooling tank; the discharge end of the cooling tank is connected to a granulation device for conveying the cooled material to the granulation device for granulation.

[0012] Preferably, a mixing tank is provided between the melting tank and the cooling tank, and is connected to both the melting tank and the cooling tank respectively; a heating device is provided in the mixing tank to maintain the required temperature of the material in the mixing tank.

[0013] Preferably, the cooling pipes in the cooling tank include an internal cooling coil and an external cooling pipe.

[0014] Preferably, the inlet of the cooling pipe is connected to the water tank on the tower, and the water tank on the tower supplies low-temperature soft water to the cooling pipe.

[0015] Preferably, the outlet of the cooling pipe is connected to the inlet of the boiler, so that the hot water from the cooling pipe is delivered to the boiler.

[0016] Preferably, the heating device is a heating pipe; the inlet of the heating pipe is connected to the steam outlet of the boiler for introducing high-temperature steam; the outlet of the heating pipe is connected to the water inlet of the boiler for conveying condensate into the boiler.

[0017] Preferably, the heating pipe includes an internal heating coil and an external insulation pipe.

[0018] This invention also provides a method for high-tower pulping and granulation of fertilizers, comprising the following steps:

[0019] (1) The materials are transported to the melting tank according to the proportion for hot melting;

[0020] (2) The melted material is fed into a mixing tank for mixing;

[0021] (3) The mixed material is transported to a cooling tank for cooling, and then granulated in a high tower.

[0022] Preferably, when the product is a 15-5-15 type compound fertilizer, the material formula is as follows: urea 31%; potassium chloride 26%; process powder 31%; monoammonium phosphate 11%; iron black powder 0.5%; borax 0.5%; wherein the nitrogen content of the urea is greater than or equal to 46%; the potassium oxide content of the potassium chloride is greater than or equal to 57%; the nitrogen content of the monoammonium phosphate is greater than or equal to 9.5%, and the phosphorus pentoxide content is greater than or equal to 47%.

[0023] When the product is a 25-10-16 type compound fertilizer, the material formula is as follows: urea 50%; potassium chloride 27.5%; process powder 1.65%; monoammonium phosphate 18.5%; potassium humate 0.1%; borax 0.25%; ammonium chloride 2%; the nitrogen content of the urea is greater than or equal to 46%; the potassium oxide content of the potassium chloride is greater than or equal to 57%; the nitrogen content of the monoammonium phosphate is greater than or equal to 11%, and the phosphorus pentoxide content is greater than or equal to 55%; the nitrogen content of the ammonium chloride is greater than or equal to 25.2%.

[0024] When the product is a 17-17-17 type compound fertilizer, the material formula is as follows: urea 33%; potassium chloride 3%; monoammonium phosphate 18.5%; monoammonium phosphate 15.75%; borax 0.25%; potassium sulfate 29.5%; wherein the nitrogen content of the urea is greater than or equal to 46%, the potassium oxide content of the potassium chloride is greater than or equal to 57%; the nitrogen content of the monoammonium phosphate is greater than or equal to 8%, and the phosphorus pentoxide content is greater than or equal to 47%; the nitrogen content of the monoammonium phosphate is greater than or equal to 11%, and the phosphorus pentoxide content is greater than or equal to 55%; and the potassium oxide content of the 52% potassium sulfate is greater than or equal to 52%. Preferably, when the product is a 15-5-15 type compound fertilizer, the temperature of the melting tank is 127℃, the temperature of the mixing tank is 113-115℃, and the temperature of the cooling tank is 107℃.

[0025] When the product is a 25-10-16 type compound fertilizer, the temperature of the melting tank is 128℃, the temperature of the mixing tank is 114-118℃, and the temperature of the cooling tank is 102℃.

[0026] When the product is a 17-17-17 type compound fertilizer, the temperature of the melting tank is 130℃, the temperature of the mixing tank is 121-126℃, and the temperature of the cooling tank is 108℃.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] Compared with products obtained by ordinary methods, the high-tower compound fertilizer produced using the system and method of this invention has significantly lower moisture content and much better caking. At the same time, due to the relatively low granulation temperature, the granulated particles are more rounded, and the number of flat particles is significantly reduced. In addition, the steam energy consumption per ton of product is also reduced. Attached Figure Description

[0029] Figure 1 This is the PID diagram for the fertilizer high-tower pulping and granulation system of this patent.

[0030] Figure 2 This is a schematic diagram of the tank structure;

[0031] Figure 3 PID diagram for a traditional high-tower granulation system for chemical fertilizers;

[0032] Figure 4 This is a diagram illustrating the low-temperature particle production process of the 25-10-16 formulation of this invention.

[0033] Figure 5 This diagram illustrates the high-temperature production process of particles using the traditional method for the 25-10-16 formula.

[0034] In the diagram: 1. Melting tank; 2. Cooling tank; 3. Mixing tank; 4. Water tank on the tower; 51. Boiler steam pipe; 52. Boiler water inlet pipe; 10. Tank body; 101. Outer insulation pipe; 102. Inner coil of the tank. Detailed Implementation

[0035] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0036] It should be noted that when an element is described as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is described as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Example

[0038] Figure 1 This invention illustrates a preferred embodiment of a high-tower fertilizer pulping and granulation system, comprising: a melting tank 1, a mixing tank 3, and a cooling tank 2. The melting tank 1 is connected to the mixing tank 3, and the mixing tank 3 is connected to the cooling tank 2. The material in the melting tank 1, after melting, enters the mixing tank 3 to mix with unmelted materials to form a pulp. The pulp in the mixing tank 3 then enters the cooling tank 2 for cooling before granulation. The melting tank 1 is equipped with a heating device for heating and melting the material within it. The cooling tank 2 is equipped with a cooling pipe for lowering the temperature of the material within it. The discharge end of the cooling tank 2 is connected to a granulation device for conveying the cooled material to the granulation device for granulation. Because of the cooling tank 2, the material is cooled, making it easier to solidify during granulation and reducing the occurrence of flat particles. Simultaneously, the cooling tank 2 allows for a higher temperature setting in the melting tank 1, which facilitates moisture evaporation and prevents particle caking due to high moisture content after granulation.

[0039] In a preferred embodiment, a mixing tank 3 is provided between the melting tank 1 and the cooling tank 2, and is respectively connected to the melting tank 1 and the cooling tank 2; a heating device is provided in the mixing tank 3 to maintain the required temperature of the material in the mixing tank 3.

[0040] like Figure 2 The illustrated tank structure includes a tank body 10; an outer insulated pipe 101; and an inner coil 102. The outer insulated pipe 101 is wound around the periphery of the tank body 10; the inner coil 102 is disposed inside the tank body 10. In this embodiment, the melting tank 1, cooling tank 2, and mixing tank 3 all have the same structure. Figure 2 The tank structure shown is different in that the outer insulation pipe 101 and the inner coil 102 of the melting tank 1 and mixing tank 3 are filled with high-temperature steam, while the cooling tank 2 is filled with low-temperature soft water.

[0041] like Figure 3 The PID diagram shown is for a traditional fertilizer high-tower pulping and granulation system. The biggest difference between this embodiment and the traditional process is that the third tank is a mixing tank, also known as a secondary mixing tank (boiler), with the same temperature as the previous mixing tank. In this embodiment, the secondary mixing tank is also called a cooling tank. Figure 1As shown in the figure, it is connected to a cold water source, which can be used to cool the cooling tank and reduce the temperature during granulation.

[0042] In a preferred embodiment, the cooling pipes in the cooling tank 2 include an internal cooling coil and an external cooling pipe. In this embodiment, the internal cooling coil corresponds to... Figure 2 The inner coil 102 shown in the diagram; the corresponding outer insulation pipe is... Figure 2 The outer cooling pipe 101 is shown.

[0043] In a preferred embodiment, the inlet of the cooling pipe is connected to the water tank 4 on the tower, which supplies low-temperature soft water to the cooling pipe. The outlet of the cooling pipe is connected to the inlet of the boiler, specifically... Figure 1 The boiler inlet pipe 52 in the middle transports hot water from the cooling pipe to the boiler. The cooling pipe can achieve the cooling effect as long as it is filled with water at a relatively low temperature. In this embodiment, the tower water tank 4 is originally used to supply water to the boiler. The water is then fed into the boiler through the cooling tank 2, which not only reduces the temperature in the cooling tank 2, but also carries the energy to the boiler, reducing the boiler's energy consumption.

[0044] In a preferred embodiment, the heating device is a heating pipe; the inlet of the heating pipe is connected to the steam outlet of the boiler, specifically... Figure 1 The boiler steam pipe 51 is used to introduce high-temperature steam; the outlet of the heating pipe is connected to the boiler water inlet, specifically... Figure 1 The boiler inlet pipe 52 is used to transport condensate to the boiler. The heating pipe includes an internal heating coil and an external insulation pipe. Correspondingly, in this embodiment, the internal heating coil corresponds to... Figure 2 The inner coil 102 in the tank; the corresponding outer insulation pipe is Figure 2 The outer insulation pipe 101 in the middle. Example

[0045] This invention also provides a method for high-tower pulping and granulation of fertilizers, comprising the following steps:

[0046] (1) The materials are transported to the melting tank according to the proportion for hot melting;

[0047] (2) The melted material is fed into a mixing tank and mixed with the non-melted material to make a pulp;

[0048] (3) The mixed material is transported to a cooling tank for cooling, and then granulated in a high tower.

[0049] Preferably, the formulation of the material is shown in Table 1; specifically, the 15-5-15 type product refers to the content of nitrogen, phosphorus pentoxide and potassium oxide being 15%, 5% and 15% respectively, and the same applies to other types.

[0050] It should be noted that the proportions in the ingredient list are weight percentages; where 46% urea refers to urea with a total nitrogen content of ≥46%; 57% potassium chloride refers to potassium oxide content of ≥57%; 9.5-47% monoammonium phosphate refers to monoammonium phosphate with a nitrogen content of ≥9.5% and phosphorus pentoxide content of ≥47%; 8-47% monoammonium phosphate refers to monoammonium phosphate with a nitrogen content of ≥8% and phosphorus pentoxide content of ≥47%; 11-55% monoammonium phosphate refers to monoammonium phosphate with a nitrogen content of ≥11% and phosphorus pentoxide content of ≥55%; 52% potassium sulfate refers to potassium oxide content of ≥52%; and 25.2% ammonium chloride refers to ammonium chloride with a nitrogen content of ≥25.2%.

[0051] Preferably, the temperatures of the cooling tank and the mixing tank are as shown in Table 3.

[0052] Combining the two types of equipment and corresponding processes in Tables 2 and 3, it can be seen that while increasing the temperature of the melting tank and mixing tank can effectively control the moisture content of the final product and prevent caking, the high temperature can also lead to problems such as… Figure 5 As shown, air bubbles easily form in the particles, or the particles are not well-formed, easily flattened, or easily broken. Using the process and equipment provided by this invention, the moisture content in the particles can be effectively reduced, preventing caking, and also preventing problems such as particles not forming properly. The produced particles are as follows: Figure 4 As shown, it has advantages such as being round and smooth, having good particle size, and producing little powder.

[0053] Combining the system of Example 1 and the method of Example 2, this invention employs an energy-saving system for the high-tower slurry preparation section of compound fertilizer. During the slurry preparation process, high-temperature steam from the boiler is introduced into the internal heating coils and external insulation pipes of both the melting tank and the mixing tank to maintain the material temperature at a relatively high and reasonable level. The high temperature evaporates the moisture in the material, reducing its moisture content. The condensate generated by steam condensation is returned to the boiler for reheating and steam recycling. Before entering the granulator, the slurry passes through a cooling tank (or, if not available, the final mixing tank is used as a cooling tank). Low-temperature soft water (which can be stored in a dedicated soft water tank on the tower) is introduced into the cooling coils and external cooling pipes of the cooling tank after boiler water treatment. This low-temperature soft water indirectly exchanges heat with the slurry, lowering its temperature to meet the granulation temperature requirements. The low-temperature soft water is pumped into the internal cooling coils and external cooling pipes of the cooling tank. Automatic control valves are installed at the outlets of these cooling coils and pipes, and their opening is controlled by the slurry temperature (or manually). The hot water generated by the heat exchange between the low-temperature soft water and the slurry is returned to the boiler to generate steam, which is used to raise the temperature of the materials in the melting tank and mixing tank.

[0054] Table 1. Fertilizer Material Formulation Table with Three Different Proportions

[0055]

[0056] Table 2. Process parameters for the pulping section in the traditional method

[0057]

[0058] Table 3. Process parameters of the pulping section of this patent

[0059]

[0060] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A fertilizer high-tower pulping and granulation system; characterized in that... include: The system comprises a melting tank, a mixing tank, and a cooling tank. The melting tank is connected to the mixing tank, and the mixing tank is connected to the cooling tank. This allows the material in the melting tank to be melted and then mixed with non-melted materials in the mixing tank to form a slurry. The slurry in the mixing tank then enters the cooling tank for cooling before granulation. The melting tank is equipped with a heating device to heat and melt the material in it. The cooling tank is equipped with a cooling pipe to lower the temperature of the material in it. The discharge end of the cooling tank is connected to a granulation device to transport the cooled material to the granulation device for granulation.

2. The fertilizer high-tower pulping and granulation system as described in claim 1, characterized in that: The mixing tank is equipped with a heating device to maintain the required temperature of the materials inside the mixing tank.

3. The fertilizer high-tower pulping and granulation system as described in claim 1, characterized in that: The cooling pipes in the cooling tank include internal cooling coils and external cooling pipes.

4. The fertilizer high-tower pulping and granulation system as described in claim 1, characterized in that: The inlet of the cooling pipe is connected to the water tank on the tower, and the water tank on the tower supplies low-temperature soft water to the cooling pipe.

5. The fertilizer high-tower pulping and granulation system as described in claim 1, characterized in that: The outlet of the cooling pipe is connected to the inlet of the boiler, so that the hot water from the cooling pipe is delivered to the boiler.

6. The fertilizer high-tower pulping and granulation system as described in claim 1 or 2, characterized in that: The heating device is a heating pipe; the inlet of the heating pipe is connected to the steam outlet of the boiler for introducing high-temperature steam; the outlet of the heating pipe is connected to the water inlet of the boiler for conveying condensate into the boiler.

7. The fertilizer high-tower pulping and granulation system as described in claim 6, characterized in that: The heating pipe includes an internal heating coil and an external insulation pipe.

8. A method for high-tower pulping and granulation of fertilizer, characterized in that, The process includes the following steps: (1) conveying the materials to the melting tank according to the proportion for hot melting; (2) conveying the hot-melted materials to the mixing tank and mixing them with the unmelted materials to make slurry; (3) conveying the mixed materials to the cooling tank for cooling, and then performing high-tower granulation after cooling.

9. The fertilizer high-tower pulping and granulation method as described in claim 8, characterized in that: When the product is a 15-5-15 type compound fertilizer, the material formula is as follows: urea 31%; potassium chloride 26%; process powder 31%; monoammonium phosphate 11%; iron black powder 0.5%; borax 0.5%; the nitrogen content of the urea is greater than or equal to 46%; the potassium oxide content of the potassium chloride is greater than or equal to 57%; the nitrogen content of the monoammonium phosphate is greater than or equal to 9.5%, and the phosphorus pentoxide content is greater than or equal to 47%. When the product is a 25-10-16 type compound fertilizer, the material formula is as follows: urea 50%; potassium chloride 27.5%; process powder 1.65%; monoammonium phosphate 18.5%; potassium humate 0.1%; borax 0.25%; ammonium chloride 2%; the nitrogen content of the urea is greater than or equal to 46%; the potassium oxide content of the potassium chloride is greater than or equal to 57%; the nitrogen content of the monoammonium phosphate is greater than or equal to 11%, and the phosphorus pentoxide content is greater than or equal to 55%; the nitrogen content of the ammonium chloride is greater than or equal to 25.2%. When the product is a 17-17-17 type compound fertilizer, the material formula is as follows: urea 33%; potassium chloride 3%; monoammonium phosphate 18.5%; monoammonium phosphate 15.75%; borax 0.25%; potassium sulfate 29.5%; the nitrogen content of the urea is greater than or equal to 46%, the potassium chloride has a potassium oxide content greater than or equal to 57%; the nitrogen content of the monoammonium phosphate is greater than or equal to 8%, the phosphorus pentoxide content is greater than or equal to 47%; the nitrogen content of the monoammonium phosphate is greater than or equal to 11%, the phosphorus pentoxide content is greater than or equal to 55%; and the potassium sulfate has a potassium oxide content greater than or equal to 52%.

10. The fertilizer high-tower pulping and granulation method as described in claim 9, characterized in that: When the product is a 15-5-15 type compound fertilizer, the temperature of the melting tank is 127℃, the temperature of the mixing tank is 113-115℃, and the temperature of the cooling tank is 107℃. When the product is a 25-10-16 type compound fertilizer, the temperature of the melting tank is 128℃, the temperature of the mixing tank is 114-118℃, and the temperature of the cooling tank is 102℃. When the product is a 17-17-17 type compound fertilizer, the temperature of the melting tank is 130℃, the temperature of the mixing tank is 121-126℃, and the temperature of the cooling tank is 108℃.

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