Method and device for reducing volatilization of granular fertilizer and improving strength

Abstract

The invention relates to a method and a device for reducing volatilization of granular chemical fertilizer and improving strength, which are suitable for granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer, the granular chemical fertilizer is treated in a vacuum packaging mode, and packaging tail gas is collected and purified. The problems of thermal decomposition volatilization, hardening, pulverization and the like of the granular fertilizer in the long-term storage process in a packaging bag are relieved, meanwhile, the strength of the granular fertilizer is improved, the fragile and pulverization characteristics of the granular fertilizer are reduced, and the long-term storage quality of the granular fertilizer product is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical fertilizer packaging and storage, and particularly relates to a method and device for reducing the volatilization of granular chemical fertilizers and improving their strength. Background Art

[0002] The ammonia-based carbon capture technology reacts ammonia absorbent with CO2 in flue gas to by-produce ammonium bicarbonate. Granular ammonium bicarbonate can be produced by extrusion granulation of ammonium bicarbonate or ammonium bicarbonate added with a modification aid. Ammonium bicarbonate-based compound fertilizers can be produced by extrusion granulation after mixing ammonium bicarbonate with one or more of phosphate fertilizers and potassium fertilizers. Granular ammonium bicarbonate and ammonium bicarbonate-based compound fertilizers are important chemical fertilizer products in China's agricultural production. Compared with the traditional organic amine process, the ammonia-based carbon capture technology can capture and sequester CO2 in the flue gas emissions and recycle it, which is of great significance for controlling and reducing greenhouse gas emissions and addressing greenhouse effect and global warming issues.

[0003] Ammonium bicarbonate is unstable in nature and is easily decomposed into carbon dioxide, ammonia and water at higher temperatures. It can be completely decomposed at 60°C and has hygroscopicity. The decomposition will accelerate after deliquescence. At present, granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizers usually adopt ordinary packaging processes, and obvious phenomena such as volatilization, decomposition and pulverization occur when heated, which affects the quality of chemical fertilizer products, has poor long-term storage effects, and is not conducive to the popularization and utilization of the by-products of the ammonia-based carbon capture system.

[0004] Patent CN210592820U reports a moisture-proof chemical fertilizer packaging system applicable to phosphate compound fertilizers, including a slurry tank, a tubular reactor, a granulator, a dryer, a cooling device and a vacuum packaging machine connected in sequence. The vacuum packaging machine is installed in a packaging room, and a dehumidifier is also provided in the packaging room. After the fertilizer is granulated and formed, it is dried, sealed and cooled and further dried, and then packaged by the vacuum packaging machine in a dedicated packaging room, and the fertilizer is basically not in contact with the outside air. This technology mainly aims at the characteristics of chemical fertilizers such as phosphate compound fertilizers being easy to absorb moisture and deliquesce, and does not solve the problems of easy volatilization, pulverization and decomposition of granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizers during storage. At the same time, it cannot solve the adverse effects of the overflow of volatile gases such as ammonia during the packaging process on the operating environment and is prone to secondary pollution. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method and device for reducing the volatilization of granular chemical fertilizers and improving their strength, which are applicable to granular ammonium bicarbonate and ammonium bicarbonate-based compound fertilizers. The technical solution is as follows:

[0006] Granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer is transported from the granulation workshop to the processing workshop. The water content in the ammonium bicarbonate of the granular fertilizer is not higher than 5%, preferably not higher than 3.5%. The particle size range of the granular fertilizer is 1 mm to 6 mm, preferably 3 mm to 5 mm. The granular fertilizer is discharged from the silo into a sealed packaging bag placed on the lower operating table. A weighing scale is set under the operating table to accurately control the weight of the granular fertilizer in the packaging bag. After the weighing and discharging are completed, the packaging bag is moved under the vacuum system, and the bag mouth is placed inside the air extraction port of the vacuum system. The operating vacuum degree of the vacuum system is set, and the built-in vacuum pump is used to complete the vacuum pumping process for the packaging bag.

[0007] After the vacuum pumping is completed, the packaging and sealing system seals the packaging bag. After sealing, the granular fertilizer packaging bag is removed from the operating table manually or mechanically. The processing workshop is equipped with a temperature and humidity control system. The temperature control system is equipped with an air conditioner, and the humidity control system is equipped with a dehumidifier to accurately control the operating temperature and humidity.

[0008] The main parameters of vacuum packaging are as follows:

[0009] (1) The operating vacuum degree is controlled at -50 kPa to -100 kPa (gauge pressure), preferably -80 to -100 kPa (gauge pressure), more preferably -90 to -100 kPa (gauge pressure);

[0010] (2) The operating temperature is controlled at 5°C to 35°C, preferably 10°C to 25°C, more preferably 15°C to 25°C;

[0011] (3) The relative humidity of the operating environment is controlled below 70%, preferably below 60%.

[0012] The granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer treated by the vacuum packaging method is stored in the vacuum packaging bag for not less than 4 hours, preferably not less than 12 hours, more preferably not less than 24 hours to improve the strength of the granular fertilizer.

[0013] The exhaust ports of the vacuum system and the packaging and sealing system are sealed and connected to the tail gas treatment system through pipelines.

[0014] The tail gas treatment system includes an air extraction pump and a bubble absorption tower, and a gas storage buffer tank can also be set as needed. After the packaging tail gas is discharged, it is transported to the gas storage buffer tank by the air extraction pump. A butterfly valve is set between the connecting pipeline of the air extraction pump and the gas storage buffer tank, and a pressure gauge is set on the gas storage buffer tank to monitor the gas pressure in the tank. The rear part of the gas storage buffer tank is connected to an exhaust pump through a connecting pipeline, and a butterfly valve is set between the connecting pipelines. The exhaust pump is connected to the bubble absorption tower, and a gas flowmeter is set on the connecting pipeline between the exhaust pump and the bubble absorption tower to control the gas flow rate and gas pressure entering the tower. The packaging tail gas is discharged into the bottom of the bubble absorption tower by the exhaust pump. After undergoing an absorption reaction with the absorption liquid in the bubble absorption tower, it is discharged to the outside atmosphere from the top of the bubble absorption tower. A demisting area is set in the upper part of the bubble absorption tower to eliminate the water vapor carried during the bubble reaction process.

[0015] The packaging tail gas mainly and particularly contains volatile components such as moisture on the particle surface, oxygen, and ammonia.

[0016] The method for reducing the volatilization of granular fertilizers and increasing their strength according to the present invention is carried out in a suitable device, preferably in a device for reducing the volatilization of granular fertilizers and increasing their strength according to the present invention.

[0017] The absorption liquid in the bubble absorption tower comes from the ammonia scrubbing tower in the ammonia-based carbon capture system. The main components of the absorption liquid solution include NH3 and NH4HCO3. The absorption liquid can also come from process water. The absorption liquid is transported into the bubble absorption tower by pipelines and a transfer pump. After the absorption process is completed, the absorption liquid is returned to the ammonia scrubbing tower in the ammonia-based carbon capture system by pipelines and a washing pump.

[0018] The tail gas treatment system can also include a water ring vacuum pump. The packaging tail gas is extracted by the water ring vacuum pump, and pollutants such as ammonia are removed due to the gas-liquid contact of the gas passing through the water ring vacuum pump. Process water is replenished through the water ring box, and the effluent is directly sent into the ammonia scrubbing tower in the ammonia-based carbon capture system for purification treatment through a pipeline.

[0019] The increase in the strength of granular fertilizers is reflected by comparing the numerical differences in the strength of granular fertilizers before and after treatment. The method for testing the strength of granules is as follows: The determination of the strength of granular fertilizers refers to the standard "Determination of the Average Compressive Strength of Nitrophosphate Granules" (GB / T 10516 - 2012). The strength is determined by a fully automatic granule strength tester using a compression test. The untreated and treated granular fertilizers are respectively placed in a container, and a compressive force perpendicular to the particle surface is applied. The deformation amount and breaking force of the granules under a certain compressive force are measured, and the strength values of different granules to be tested are automatically read by the instrument.

[0020] The strength (Newton, N) of the granular fertilizers treated by the method and device for reducing the volatilization of granular fertilizers and increasing their strength according to the present invention increases by at least 20%, preferably at least 25%, more preferably at least 35%, and most preferably at least 40%.

[0021] The reduction of volatilization of granular chemical fertilizers is obtained by testing the decomposition rate of granular chemical fertilizers before and after treatment. The test method for the decomposition rate of granular chemical fertilizers is as follows: The decomposition rate of granular chemical fertilizers is determined by the weighing method. The volatilization decomposition of ammonium bicarbonate will produce NH3, H2O and CO2, resulting in a decrease in weight. Weigh a certain weight of granular chemical fertilizers with and without vacuum treatment respectively, place them in an incubator to control a constant temperature (25 °C), and after storing for a certain period of time (30 days), take them out and weigh again. The decomposition rate of the granular chemical fertilizer is the ratio of the weight loss to the original weight.

[0022] The decomposition rate of the granular chemical fertilizer treated by the method and device for reducing the volatilization and increasing the strength of the granular chemical fertilizer according to the present invention remains basically unchanged, preferably remains unchanged.

[0023] This application also relates to the following implementation schemes:

[0024] 1. A method for reducing the volatilization and increasing the strength of granular chemical fertilizers, characterized in that it uses a vacuum packaging method to treat granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizers, reduces the concentrations of components such as oxygen concentration, humidity, and volatile components on the surface of the granules in the packaging bag, reduces problems such as decomposition and volatilization, caking, powdering, and breaking during storage, transportation, and use, and at the same time increases the strength and slow-release ability of the granular chemical fertilizers.

[0025] 2. The method according to implementation scheme 1, characterized in that it uses a packaging bag with airtight performance, and a vacuum system evacuates the packaging bag.

[0026] 3. The method according to implementation scheme 1, characterized in that the ammonium bicarbonate in the granular chemical fertilizer comes from an ammonia-based carbon capture system.

[0027] 4. The method according to implementation scheme 1, characterized in that the water content in the ammonium bicarbonate in the granular chemical fertilizer is not higher than 5%, preferably not higher than 3.5%.

[0028] 5. The method according to implementation scheme 1, characterized in that the granular ammonium bicarbonate is formed by extrusion granulation of ammonium bicarbonate or ammonium bicarbonate added with a modifying agent.

[0029] 6. The method according to implementation scheme 1, characterized in that the ammonium bicarbonate-based compound fertilizer in the granular chemical fertilizer is formed by extrusion granulation after mixing ammonium bicarbonate with one or more of phosphate fertilizers, potassium fertilizers, etc.

[0030] 7. The method according to implementation scheme 1, characterized in that it further includes using an exhaust gas treatment system to remove the volatile gas ammonia extracted during the packaging process.

[0031] 8. The method according to implementation scheme 7, characterized in that the exhaust gas treatment system removes the volatile gas ammonia extracted during the packaging process by using a bubbling absorption process with a bubbling absorption liquid.

[0032] 9. The method according to embodiment 7, characterized in that the washing liquid of the bubbling absorption process in the tail gas treatment system is returned to the ammonia-based carbon capture system.

[0033] 10. The method according to embodiment 1, characterized in that for the granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer treated by vacuum packaging, the storage environmental temperature should be less than or equal to 30 °C, preferably less than or equal to 20 °C.

[0034] 11. The method according to embodiment 7, characterized in that the tail gas treatment system includes a liquid ring vacuum pump, and the packaging tail gas is extracted by the liquid ring vacuum pump, while removing the volatile gas ammonia extracted during the packaging process.

[0035] 12. The method according to embodiment 11, characterized in that the liquid ring vacuum pump is replaced by process water make-up, and the effluent goes to the ammonia-based carbon capture system.

[0036] 13. The method according to embodiment 2, characterized in that the vacuum system includes a liquid ring vacuum pump, and the packaging tail gas is extracted by the liquid ring vacuum pump.

[0037] 14. The method according to embodiment 8, characterized in that the bubbling absorption liquid is provided by the process water system.

[0038] 15. The method according to embodiment 1, characterized in that the volatile components are the surface moisture, oxygen, and ammonia of the granular fertilizer.

[0039] 16. A device for reducing the volatilization of granular fertilizer and increasing its strength, characterized by comprising:

[0040] (1) A vacuum system for evacuating the granular fertilizer;

[0041] (2) A packaging sealing system for sealing the airtight packaging bag;

[0042] (3) A tail gas treatment system for treating the gas extracted during operations (1) and (2);

[0043] (4) A temperature and humidity control system for controlling the temperature and humidity of (1) and (2);

[0044] By integrally enclosing (1) and (2) and connecting them to (3) through pipelines.

[0045] 17. The device according to embodiment 16, characterized in that the tail gas treatment system includes

[0046] (1) An air extraction pump for extracting the packaging tail gas from the vacuum packaging system;

[0047] (2) The bubble absorption tower is used to purify the packaging exhaust gas.

[0048] 18. The device according to embodiment 16, characterized in that the tail gas treatment system includes a gas storage buffer tank for storing the packaging tail gas extracted from the vacuum packaging system.

[0049] 19. The device according to embodiment 16, characterized in that the temperature and humidity control system includes an air conditioner and a dehumidifier to control the temperature and humidity.

[0050] 20. The device according to embodiment 17, characterized in that the bubble absorption tower operates intermittently, and the gas entering the tower comes from the packaging tail gas stored in the gas storage buffer tank.

[0051] 21. The device according to embodiment 16, characterized in that the bubble absorption tower is connected to the ammonia-based carbon capture system. The absorption liquid of the bubble absorption tower is provided by the ammonia-based carbon capture system. After the absorption is completed, the absorption liquid returns to the ammonia-based carbon capture system.

[0052] 22. The device according to embodiment 17, characterized in that the bubble absorption tower is connected to the process water system and the ammonia-based carbon capture system. The absorption liquid of the bubble absorption tower is provided by the process water system. After the absorption is completed, the absorption liquid returns to the ammonia-based carbon capture system.

[0053] 23. The device according to embodiment 16, characterized in that the tail gas treatment system includes a water-ring vacuum pump, and the water-ring vacuum pump is connected to the process water system and the ammonia-based carbon capture system. Description of the Drawings

[0054] Figure 1 is a schematic diagram according to the technical solution of the present invention,

[0055] Figure 2 is a schematic diagram according to the technical solution of the present invention,

[0056] wherein the reference numerals are as follows:

[0057] 1. Ammonia-based carbon capture system; 2. Granulation system; 3. Feeding system; 4. Packaging and sealing system; 5. Vacuum system; 6. Temperature and humidity control system; 7. Enclosed system; 8. Air extraction pump; 9. Gas storage buffer tank; 10. Treated granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer; 11. Bubble absorption tower; 12. Washing pump; 13. Water-ring vacuum pump; 14. Water-ring tank; 15. Process water.

[0058] Example 1:

[0059] As Figure 1, the ammonium bicarbonate product of the ammonia-based carbon capture system enters the granulation system 2, and the ammonium bicarbonate-based compound fertilizer produced is controlled by the granulation system 2 to have a water content in the ammonium bicarbonate in the granular fertilizer not higher than 3%, and the particle size range of the granular fertilizer is 3 mm to 5 mm. The granular fertilizer enters the feeding system 3, and is discharged from the silo into a sealed packaging bag placed on the lower operating platform. A weighing scale is set under the operating platform, and the weighing scale precisely controls the weight of the granular fertilizer in the packaging bag. After the weighing and discharging are completed, the packaging bag is moved to the packaging and sealing system 4, and the bag mouth is placed inside the air extraction port of the vacuum system 5. The vacuum system 5 sets the operating vacuum degree, and the built-in vacuum pump completes the vacuuming process for the packaging bag.

[0060] After the vacuuming is completed, the packaging and sealing system 4 seals the packaging bag. After the sealing is completed, the granular fertilizer 10 is removed from the operating platform manually or mechanically in the packaging bag. The device is provided with a temperature and humidity control system 6. The temperature control system is equipped with an air conditioner, and the humidity control system is equipped with a dehumidifier to precisely control the operating temperature and humidity.

[0061] The main parameters of the vacuum packaging are as follows:

[0062] (1) The operating vacuum degree is controlled at -90 to -100 kPa (gauge pressure);

[0063] (2) The operating temperature is controlled at 15°C to 25°C;

[0064] (3) The relative humidity of the operating environment is controlled below 60%.

[0065] The vacuum system 5 and the packaging and sealing system 4 are isolated through the closed system 7 and are connected to the tail gas treatment system through pipelines.

[0066] The tail gas treatment system includes an air extraction pump 8, a bubbling absorption tower 11, and a gas storage buffer tank 9. After the packaging tail gas is discharged, it is transported to the gas storage buffer tank 9 by the air extraction pump 8. A butterfly valve is set between the connecting pipeline of the air extraction pump and the gas storage buffer tank, and a pressure gauge is set on the gas storage buffer tank to monitor the gas pressure in the tank. The rear of the gas storage buffer tank is connected to an exhaust pump through a connecting pipeline, and a butterfly valve is set between the connecting pipelines. The exhaust pump is connected to the bubbling absorption tower 11, and a gas flow meter is set on the connecting pipeline between the exhaust pump and the bubbling absorption tower to control the gas flow rate and gas pressure entering the tower. The packaging tail gas is discharged into the bottom of the bubbling absorption tower by the exhaust pump, and after undergoing an absorption reaction with the absorption liquid in the bubbling absorption tower, it is discharged to the outside atmosphere from the top of the bubbling absorption tower. A demisting area is set in the upper part of the bubbling absorption tower to remove the water vapor carried during the bubbling reaction process.

[0067] The absorption liquid of the bubbling absorption tower comes from the ammonia washing tower in the ammonia-based carbon capture system. The main components of the absorption liquid solution include NH3 and NH4HCO3, and are transported to the bubbling absorption tower through pipelines and transfer pumps. The absorption liquid of the bubbling absorption tower can also be directly supplemented with process water. After the absorption process is completed, the absorption liquid returns to the ammonia washing tower in the ammonia-based carbon capture system through pipelines and washing pumps.

[0068] Comparison of ammonium bicarbonate-based compound fertilizer granules before and after vacuum treatment:

[0069] Serial number Item Unit Before treatment After treatment 1 Strength N 12.06 14.71 2 Decomposition rate (25°C, 30 days) ％ 0.5 No change

[0070] Example 2:

[0071] As Figure 2 , the tail gas treatment system is different from that in Example 1 and includes a water-ring vacuum pump 13, a water-ring tank 14, and process water 15. The packaging tail gas is extracted by the water-ring vacuum pump 13. The gas passing through the water-ring vacuum pump removes pollutants such as ammonia due to the gas-liquid contact in the water-ring tank and is discharged to the outside atmosphere from the top of the water-ring tank. The process water 15 is replenished through the water-ring tank 14, and the effluent is directly sent into the ammonia scrubbing tower of the ammonia-based carbon capture system 1 for purification treatment through a pipeline.

[0072] The data of the comparison of ammonium bicarbonate-based compound fertilizer granules before and after vacuum treatment in Example 2 are the same as those in Example 1.

[0073] From the results of the above Examples 1 and 2, it can be seen that the strength of the granular fertilizers treated by the method and device for reducing the volatilization and increasing the strength of granular fertilizers of the present invention is significantly increased while the decomposition rate remains unchanged.

[0074] Only the above-mentioned are the preferred embodiments of the present invention. Those skilled in the art who are familiar with this technology can naturally make changes according to actual needs under the guidance of the present invention after understanding the technical means of the present invention. Therefore, all equivalent changes and modifications made according to the scope of the patent application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. A method for reducing the volatilization of granular chemical fertilizers and increasing the strength, characterized in that, The granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer is treated by vacuum packaging, reducing the concentrations of components such as oxygen, humidity, and volatile components on the surface of the particles in the packaging bag, reducing problems such as decomposition and volatilization, caking, powdering, and fragmentation during storage, transportation, and use, and at the same time improving the strength and slow-release ability of the granular chemical fertilizer.

2. The method according to claim 1, wherein , A packaging bag with airtight performance is used, and the vacuum system evacuates the packaging bag.

3. The method according to claim 1, wherein , The ammonium bicarbonate in the granular chemical fertilizer comes from an ammonia-based carbon capture system.

4. The method according to claim 1, characterized in that , The water content in the ammonium bicarbonate in the granular chemical fertilizer is not higher than 5%, preferably not higher than 3.5%.

5. The method according to claim 1, wherein , The granular ammonium bicarbonate is formed by extrusion granulation of ammonium bicarbonate or ammonium bicarbonate added with a modifying agent.

6. The method according to claim 1, characterized in that , The ammonium bicarbonate-based compound fertilizer in the granular chemical fertilizer is formed by extrusion granulation after mixing ammonium bicarbonate with one or more of phosphate fertilizer, potassium fertilizer, etc.

7. The method according to claim 1, wherein , It also includes using an exhaust gas treatment system to remove the volatile gas ammonia extracted during the packaging process.

8. The method according to claim 7, characterized in that, The exhaust gas treatment system removes the volatile gas ammonia extracted during the packaging process by using a bubbling absorption process with a bubbling absorption liquid.

9. The method according to claim 7, wherein The washing liquid of the bubbling absorption process in the exhaust gas treatment system is returned to the ammonia-based carbon capture system.

10. The method according to claim 1, characterized in that For the granular ammonium bicarbonate or ammonium bicarbonate-based compound fertilizer treated by the vacuum packaging method, the storage environmental temperature should be less than or equal to 30°C, preferably less than or equal to 20°C.

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