Production method of selenium-rich fertilizer
By using soluble selenium raw materials on the conventional roller granulation fertilizer production line to make a solution or suspension, and spraying it on the finished pellet fertilizer with a sprayer, the huge starting volume, viscous loss and high temperature volatility in the existing technology have been solved, and stable, safe and efficient production of selenium-rich fertilizers has been achieved.
Patent Information
- Application Number
- CN202411937587.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-03-14
AI Technical Summary
The existing selenium-rich fertilizer production technology has huge starting problems, viscosity raw materials loss, volatile losses caused by selenium elements to be sensitive to high temperatures, solid selenium raw materials blocking the feeding funnel and the risk of dust flying.
A conventional drum granulation fertilizer production line is used to make a solution or suspension by stirring the soluble selenium raw material with water, spraying it onto the surface of the finished granular fertilizer with a water pump sprayer, and mix it thoroughly with the conveyor belt and the drum production line to avoid the high-temperature drying process.
The minimum starting volume is reduced to 500 kg, avoiding the loss of selenium element caused by viscosity raw materials and high-temperature drying, solving the problems of selenium raw materials blockage and dust flying, and achieving stable, safe and efficient production of selenium-rich fertilizers.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of production of functional agricultural selenium-rich fertilizers, and in particular to a production method of selenium-rich fertilizers. Background Art
[0002] Selenium is an essential trace element for humans and animals, and is also a trace element beneficial to plant growth.
[0005] There are two main ways to grow selenium-rich agricultural products: root fertilization and foliar spraying. For root fertilization, granular selenium fertilizer that can be spread by drones is the most widely used. Currently, granular selenium fertilizer production generally adds selenium to conventional fertilizers and uses conventional fertilizers as a carrier to apply selenium to the soil.
[0006] According to the current production technology, there are two main ways to add selenium raw materials to granular fertilizers: one is to add selenium raw materials to powdered raw materials by first mixing the selenium raw materials with other powdered raw materials and then forming granules together; the other is to add the powdered selenium raw materials directly to the finished granular fertilizer before packaging.
[0007] The disadvantage of the first method is that the initial production volume is large. The granular fertilizer production line is huge and lengthy. Once the production starts from the powdered raw materials, it starts at 100 tons, and the initial production must reserve about ten tons of fixed raw material losses as the viscous consumption of the entire production line. The production rules require continuous operation to produce the same fertilizer as much as possible, and the fertilizer variety cannot be switched at will. Selenium-containing fertilizer is a trace element fertilizer. There is often a demand for multiple batches of different selenium content varieties with small production volumes. This demand is inconsistent with the large production volume and continuous operation characteristics of the granular fertilizer production line. In addition, there is a high-temperature drying process in the granulation process of some granular fertilizers. For example, in the production process of granular organic fertilizers, the newly produced granular fertilizers with high humidity will be passed through a high-temperature drying drum at several hundred degrees Celsius. Selenium is sensitive to high temperatures, and high temperatures can easily cause selenium volatilization and loss.
[0008] The disadvantage of the second method is that the solid selenium raw material is an extremely fine powder with strong adhesion and easy moisture absorption. When the powdered selenium raw material is directly added to the finished particles, it can only be discharged slowly through the small funnel discharge port by its own weight, which will inevitably cause the selenium raw material to block the feeding funnel and cannot be fed evenly and stably. In addition, this method will cause the problem of selenium raw material dust flying in the process of adding selenium raw material to the feeding funnel and unblocking the blocked funnel during operation, which can easily cause workers' skin to come into contact with selenium raw material dust, resulting in the risk of poisoning, and causing the loss of selenium raw material flying. Summary of the invention
[0009] In view of this, the present invention provides a method for producing selenium-rich fertilizer based on the basic knowledge of a conventional drum granulation fertilizer production line, comprising the following steps: 1) Calculate the usage of soluble selenium raw materials according to the selenium content target of the finished granular fertilizer, and calculate the dilution multiple of the selenium raw materials according to the spraying speed of the sprayer; 2) Stirring the soluble selenium raw material and water according to the calculated dilution multiple to form a solution or suspension; 3) putting the solution or suspension obtained in step 2) into a liquid storage bucket; 4) First put the water inlet pipe of the water pump sprayer into the liquid bucket, and then put the liquid bucket on the scale. The spray speed of the sprayer must be calibrated when using it for the first time; 5) Install the belt scale under the conveyor belt and adjust the conveying speed of the conveyor belt; 6) When the particles are transported on the conveyor belt, the amount of solution to be sprayed per unit time is calculated according to the weight of the particles transported per unit time displayed on the belt scale, the spraying speed is adjusted to this value, and the selenium solution is sprayed on the surface of the particles; 7) During the operation, the stability of production needs to be monitored from time to time; 8) The granular fertilizer sprayed with selenium solution passes through the conveyor belt and falls into the drum. After being rotated and fully mixed in the drum, it is transferred to the baler and can be packaged and shipped out of the warehouse. (Note: The roller between the conveyor belt and the baler is an inherent equipment on the fertilizer production line and does not belong to the accessories that need to be purchased separately in the present invention.
[0010] Preferably, in the production method as described above, in step 1), the selenium raw material used is a water-soluble raw material or a raw material that can form a suspension under liquid conditions. It can be one or any combination of amino acid chelated selenium, ultrafine activated mineral powder, selenate, selenite, selenoamino acid, and selenium-enriched yeast.
[0011] Preferably, in the method as described above, in step 2), the selenium raw material must be dissolved in water at a lower dilution multiple according to its water solubility, and the prepared solution or suspension can smoothly pass through the filter screen of the water inlet pipe of the sprayer.
[0012] Preferably, in the method as described above, in step 3), the liquid storage barrel used is a plastic barrel instead of a metal barrel, the volume of the plastic barrel is 30-150L, the opening of the plastic barrel is 10-100 cm, and the barrel needs to include a plastic cover that can be opened and covered to reduce dust falling into the barrel during operation.
[0013] Preferably, in the method described above, in step 4), the platform scale used is an ordinary commercial flat-bottom scale, and the weighing surface of the scale needs to be able to place the liquid barrel relatively loosely, and the placement order is: first reset the platform scale reading to zero, then place the liquid barrel, then put the sprayer water inlet pipe into the liquid barrel, and then cover the liquid barrel lid. After this sequence is completed, the weight reading displayed on the platform scale is the total weight of "solution + barrel body + barrel cover + water inlet pipe".
[0014] Preferably, in the method as described above, in step 4), it is necessary to calibrate the spray rate of the sprayer first, and the test method is: record the initial reading and time of the scale, record the end reading and time of the scale after spraying for a period of time, calculate the average spray rate of the time period based on the scale reading, and compare the average spray rate with the instantaneous spray rate on the flow meter. If the average spray rate is consistent with the instantaneous spray rate (within the allowable error range), the calibration is completed. If they are inconsistent, the spray rate based on the scale reading must be used as the standard, and the deviation of the flow meter must be calibrated to make it consistent with the spray rate based on the scale.
[0015] Preferably, in the method as described above, in step 5), a trumpet-shaped wind shield equal to the width of the conveyor belt is installed on the nozzle at the top of the spray rod, and the nozzle in the wind shield is inverted on the particles. There is only a very small gap between the wind shield and the particle surface of the conveyor belt, and no spray will float out, causing waste of raw materials.
[0016] Preferably, in the method described above, in step 6), the amount of solution to be sprayed per unit time is calculated based on the weight of the particles transported per unit time displayed on the belt scale. If the transmission rate of the granular fertilizer on the conveyor belt fluctuates, the solution spraying rate must be adjusted synchronously through the flow control valve according to the change in the reading on the belt scale, so that the liquid flow meter reading and the belt scale reading are synchronized.
[0017] Preferably, in the method described above, in step 7), when a barrel of solution is nearly finished being sprayed, the readings of the platform scale and the belt scale shall be used as the basis, and the total amount of solution sprayed and the total weight of the particles sprayed within the initial and final time intervals of spraying the barrel of solution shall be counted again. The average selenium content of the particles within the time interval is calculated based on the total amount of solution sprayed and the total weight of the granular fertilizer sprayed. If the average selenium content is consistent with the set selenium content, the system is normal. If the average selenium content and the set selenium content exceed the error range, the solution spraying speed shall be slowed down or accelerated according to whether the actual selenium content is too high or too low.
[0018] Preferably, in the equipment and method for producing selenium-rich fertilizer as described above, in step 8), the granular fertilizer sprayed with selenium solution passes through a conveyor belt and falls into a drum, where it rotates to be fully mixed and evenly contacted, and then is transferred to a packaging machine for packaging.
[0019] Compared with the prior art, the improvement effect of the present invention is: 1) Compared with the prior art of adding selenium raw materials to powdery raw materials to start granulation, the method provided by the present invention avoids the problem of huge starting amount. Conventional finished granular fertilizer can be directly added. According to this method, the minimum starting amount can be reduced to 500 kg, and the demand of multiple batches of production and stopping at any time can be met; 2) Compared with the prior art of starting granulation by adding selenium raw materials from powdered raw materials, the method of the present invention eliminates the loss of sticky raw materials when the granulation production line is first started. In this method, the loss of both granular fertilizer and selenium raw materials is close to zero; 3) Compared with the prior art of adding selenium raw materials to powdered raw materials to start granulation, the method provided by the present invention avoids the high-temperature drying process. The method allows the selenium raw materials to be directly added to the cooled finished granules, so the loss of selenium raw materials in the high-temperature drying drum is zero; 4) Compared with the prior art of directly adding powdered selenium raw materials to finished particles, the method provided by the present invention eliminates the problem of selenium raw materials blocking the feeding funnel and failing to feed evenly and stably. In the present method, the solid selenium raw materials are first made into a solution or suspension, and the device of the present invention can be stably and smoothly sprayed into the finished particles; 5) Compared with the prior art of directly adding powdered selenium raw materials to finished particles, the method provided by the present invention eliminates the problem of dust loss of solid selenium raw materials during the process of adding selenium raw materials to the feeding funnel and unclogging the blocked funnel during the operation; 6) The method provided by the present invention and the equipment parts used in the method can all be easily purchased from the market, with low cost and easy installation. They are compatible with the production lines of various fertilizer factories and are easy to install and disassemble. Selenium fertilizer, as a functional fertilizer, is a customized fertilizer with a strong targeted use surface. It is generally produced and used immediately according to demand. The equipment in the method occupies a small area and can be temporarily installed to meet production needs when there are production needs. It can be easily disassembled and stored when the production needs end, and has good application prospects. DETAILED DESCRIPTION
[0020] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Example
[0021] This embodiment provides a method for producing selenium-rich fertilizer.
[0022] In the present embodiment 1, a chelated selenium raw material with a selenium content of 100000 mg / kg was used, and a conventional drum granulation fertilizer production line was utilized to produce 300 tons of selenium-rich organic fertilizers. The finished product selenium-rich organic fertilizer index requirement was "selenium content ≥100 mg / kg, moisture ≤15%, organic matter ≥30%, and total nutrients ≥4%". The granular organic fertilizer index produced by the conventional production line before the spraying solution was "selenium content=0 mg / kg, moisture=10%, organic matter=32%, and total nutrients=4.3%".
[0023] The operation steps according to the present invention are as follows: Step 1: In this embodiment, the chelated selenium raw material can form a suspension with water in a ratio of 1:3. The selenium content of the suspension prepared in this embodiment = 100000 / 4 = 25000 mg / kg. In actual operation, the selenium content in the target particles is set to 110 mg / kg. The amount of solution to be sprayed per 1 kg of initial particles is 1*110 / 250000=0.0044kg, 75% of the solution is water, then the theoretical content of the final product can be calculated as "selenium content = 110mg / kg, water = (0.1+0.0044*0.75) / 1.0044=10.3%, organic matter = 0.32 / 1.0044=31.8%, total nutrients = 0.043 / 1.0044=4.28%", the theoretical value can meet the requirements of "selenium content ≥100mg / kg, water ≤15%, organic matter ≥30%, total nutrients ≥4%"; Step 2: Prepare a suspension with a selenium content of 25000 mg / kg according to the ratio of selenium raw material to water = 1:3; Step 3: Take 50 kg of the prepared suspension and put it into a 100 L plastic liquid barrel; Step 4: Since the flow rate unit of the flow meter is "L / minute", it needs to be converted into "kg / minute". The operation method is: place the liquid bucket on the scale, put the water inlet pipe of the water pump sprayer into the liquid bucket, then cover the liquid bucket, and place the liquid bucket on the scale. At this time, the reading displayed on the scale is "54kg", which means that the total weight on the scale is 54kg, that is, "initial solution + barrel body + barrel cover + water inlet pipe = 54kg", turn on the sprayer (the solution sprayed during the test is sprayed into another spare liquid bucket), and start the stopwatch at the same time, and turn off the spray after 5 minutes of spraying. The scale reading is 49.6kg, that is, "remaining solution + barrel body + barrel cover + water inlet pipe = 49.6kg", then the amount of solution sprayed in 5 minutes = 54-49.6 = 4.4kg, average spray speed = 4.4 / 5 = 0.88kg / minute, the flow meter instrument panel can simultaneously display the instantaneous flow rate, average flow rate, and the total amount of interval spraying. At this time, the flow meter reading is "instantaneous flow rate = 0.8L / minute, average flow rate = 0.8L / minute g, total amount of interval spraying = 4L", which can be converted to 1L / minute = 1.1kg / minute. Repeat the calibration three times according to this operation and take the average of the three data; Step 5: Install the belt scale under the conveyor belt and turn it on. Put granular fertilizer on the conveyor belt. The reading on the belt scale is 200kg / minute, which means that the weight of granular fertilizer passing through the cross section of the conveyor belt per minute is 200kg; Step 6: In this example, the selenium content of the fertilizer is designed to be 110 mg / kg, and the selenium content of the solution is 25000 mg / kg. Then, the weight of the solution to be sprayed for 200 kg of granular fertilizer = 200*110 / 25000 = 0.88 kg, that is, the spraying speed needs to be set to 0.88 kg / minute. According to the calibration data in step 4, the corresponding flow meter reading is 0.88 / 1.1 = 0.8 L / minute. Turn on the sprayer, adjust the flow control valve, so that the flow meter reading shows 0.8 L / minute, spray the solution onto the conveyor belt particles, and start the operation. When a bucket of solution is almost finished, add new solution to the bucket. The sprayer does not need to be interrupted in the middle and can continue to operate; Step 7: During the operation, the stability of production needs to be monitored from time to time. Operation method: When a barrel of solution starts to spray, record the initial time, and record the initial reading of the platform scale and the initial reading of the belt scale at the same time. When the barrel of solution is almost finished spraying, record the end time, and record the end reading of the platform scale and the end reading of the belt scale at the same time. Calculate the total amount of solution sprayed in the time interval through the initial reading and end reading of the platform scale, calculate the total amount of granular fertilizer sprayed in the time interval through the initial reading and end reading of the belt scale, and calculate the actual content of the product produced in the interval. If it is within the error range, the system is in a stable operating state. If it exceeds the error range, it is necessary to pass the flow valve , adjust the spray speed of the sprayer to make the content reach the target value, Note 1: The platform scale and belt scale are large mechanical structures for stable weighing, and their readings can be visually verified by physical materials at any time, while the flow meter is a small precision device for weighing the volume flow rate of liquids. The readings may have errors, and the readings are not easy to be visually verified by physical materials at any time. Therefore, the evaluation of the system's operating stability must be based on the platform scale and belt scale; Note 2: The frequency of scheduled monitoring needs to be adjusted according to actual conditions. If the system stability is good, the monitoring frequency can be reduced. If the system stability is poor, the monitoring frequency needs to be increased; Step 8: The granular fertilizer sprayed with selenium solution falls into the drum after passing through the conveyor belt. After being rotated in the drum to be fully mixed and evenly contacted, it is transferred to the baler and can be packaged and shipped out. Note: The roller between the conveyor belt and the baler is an inherent equipment installed on the fertilizer production line and does not belong to the accessories that need to be purchased separately in the present invention.
[0024] After production, 5 samples were randomly selected from different locations to test the selenium content. The sample data are as follows in Table 1: Table 1
[0025] The actual test indicators can meet the product requirements.
[0026] Example 2 In this Example 2, a selenium raw material in the form of selenite with a selenium content of 300,000 mg / kg was used, and a conventional drum granulation compound fertilizer production line was used to produce 20 tons of selenium-containing granular compound fertilizer. The index requirements of the finished selenium-containing granular compound fertilizer were "selenium content ≥ 100 mg / kg, moisture ≤ 1.5%, total nutrients ≥ 45%", and the index requirements of ordinary granular compound fertilizer before spraying the solution were "selenium content = 0 mg / kg, moisture = 0.6%, total nutrients = 48%".
[0027] The operation steps according to the present invention are as follows: Step 1: In this embodiment, the selenium raw material in the form of selenite can form a completely water-soluble solution with water in a ratio of 1:2. The selenium content of the solution configured in this embodiment = 300000 / 3 = 100000 mg / kg. In actual operation, the selenium content in the target particles is set to 110 mg / kg. The amount of solution to be sprayed per 1 kg of initial particles is 1*110 / 100000=0.0011 kg. 67% of the solution is water. The theoretical content of the final product can be calculated as "selenium content = 110 mg / kg, water = (0.006+0.0011*0.67) / 1.0011=0.67%, total nutrients = 0.48 / 1.0011=47.9%", and the theoretical value can meet the requirements of "selenium content ≥ 100 mg / kg, water ≤ 1.5%, total nutrients ≥ 45%"; Step 2: Prepare a suspension with a selenium content of 100,000 mg / kg according to the ratio of selenium raw material to water = 1:2; Step 3: Take 50 kg of the prepared suspension and put it into a 100 L plastic liquid barrel; Step 4: Since the flow rate unit of the flow meter is "L / minute", it needs to be converted into "kg / minute". The operation method is: place the liquid bucket on the scale, put the water inlet pipe of the water pump sprayer into the liquid bucket, then cover the liquid bucket, and place the liquid bucket on the scale. At this time, the reading displayed on the scale is "54kg", which means that the total weight on the scale is 54kg, that is, "initial solution + barrel body + barrel cover + water inlet pipe = 54kg", turn on the sprayer (the solution sprayed during the test is sprayed into another spare liquid bucket), and start the stopwatch at the same time. Turn off the sprayer after 5 minutes of spraying. The scale reading is 49.3kg, that is, "remaining solution + barrel body + barrel cover + water inlet pipe = 49.3kg", then the amount of solution sprayed in the 5 minutes = 54-49.3 = 4.7kg, the average spray rate = 4.7 / 5 = 0.94kg / minute, the flow meter instrument panel can simultaneously display the instantaneous flow rate, average flow rate, and the total amount of interval spraying. At this time, the flow meter reading is "instantaneous flow rate = 0.81L / minute, average flow rate = 0.81L / minute, interval spraying total amount = 4.05L", which can be converted to a flow meter of 1L / minute = 1.16kg / minute. Repeat the calibration three times according to this operation and take the average of the three data; Step 5: Install the belt scale under the conveyor belt and turn it on. Put granular fertilizer on the conveyor belt and adjust the reading on the belt scale to 180kg / min, which means that the weight of granular fertilizer passing through the cross section of the conveyor belt per minute is 180kg; Step 6: In this example, the selenium content of the fertilizer is designed to be 110 mg / kg, and the selenium content of the solution is 100000 mg / kg. The weight of the solution to be sprayed for 180 kg of granular fertilizer = 180*110 / 100000 = 0.198 kg, that is, the spray rate needs to be set to 0.198 kg / minute. According to the calibration data in step 4, the corresponding flow meter reading is 0.198 / 1.1 = 0.18 L / minute. Turn on the sprayer, adjust the flow control valve, so that the flow meter reading shows 0.18 L / minute, spray the solution onto the conveyor belt particles, and start the operation. When a bucket of solution is almost finished, add new solution to the bucket. The sprayer does not need to be interrupted in the middle and can continue to operate; Step 7: During the operation, the stability of production needs to be monitored from time to time. Operation method: When a barrel of solution starts to spray, record the initial time, and record the initial reading of the platform scale and the initial reading of the belt scale at the same time. When the barrel of solution is almost finished spraying, record the end time, and record the end reading of the platform scale and the end reading of the belt scale at the same time. Calculate the total amount of solution sprayed in the time interval through the initial reading and end reading of the platform scale, calculate the total amount of granular fertilizer sprayed in the time interval through the initial reading and end reading of the belt scale, and calculate the actual content of the product produced in the interval. If it is within the error range, the system is in a stable operating state. If it exceeds the error range, it is necessary to pass the flow valve , adjust the spray speed of the sprayer to make the content reach the target value, Note 1: The platform scale and belt scale are large mechanical structures for stable weighing, and their readings can be visually verified by physical materials at any time, while the flow meter is a small precision device for weighing the volume flow rate of liquids. The readings may have errors, and the readings are not easy to be visually verified by physical materials at any time. Therefore, the evaluation of the system's operating stability must be based on the platform scale and belt scale; Note 2: The frequency of scheduled monitoring needs to be adjusted according to actual conditions. If the system stability is good, the monitoring frequency can be reduced. If the system stability is poor, the monitoring frequency needs to be increased; Step 8: The granular fertilizer sprayed with selenium solution falls into the drum after passing through the conveyor belt. After being rotated in the drum to be fully mixed and evenly contacted, it is transferred to the baler and can be packaged and shipped out. Note: The roller between the conveyor belt and the baler is an inherent equipment installed on the fertilizer production line and does not belong to the accessories that need to be purchased separately in the present invention.
[0028] After production, 5 samples were randomly selected from different locations to test the selenium content. The sample data are as shown in Table 2: Table 2
[0029] The actual test indicators can meet the product requirements.
[0030] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A method for producing selenium-rich fertilizer, which is realized by adding additional equipment and methods on the basis of a conventional drum granulation fertilizer production line, characterized in that The following steps are involved: 1) Calculate the usage of soluble selenium raw materials according to the selenium content target of the finished granular fertilizer, and calculate the dilution multiple of the selenium raw materials according to the spray speed of the sprayer; 2) Stirring the soluble selenium raw material and water according to the calculated dilution multiple to form a solution or suspension; 3) putting the solution or suspension obtained in step 2) into a liquid storage bucket; 4) First put the water inlet pipe of the water pump sprayer into the liquid bucket, and then put the liquid bucket on the scale. The spray speed of the sprayer must be calibrated when using it for the first time; 5) Install the belt scale under the conveyor belt and adjust the conveyor belt conveying speed; 6) When the particles are transported on the conveyor belt, the amount of solution to be sprayed per unit time is calculated according to the weight of the particles transported per unit time displayed on the belt scale, the spraying speed is adjusted to this value, and the selenium solution is sprayed on the surface of the particles; 7) During the operation, the stability of production needs to be monitored from time to time; 8) The granular fertilizer sprayed with selenium solution falls into the drum after passing through the conveyor belt. After being rotated and fully mixed in the drum, it is transferred to the packaging machine for packaging and shipment.
2. The method according to claim 1, characterized in that The selenium raw material is a water-soluble selenium-containing raw material that can form a suspension under liquid conditions.
3. The method according to claim 1, characterized in that The selenium raw material is one or any combination of amino acid chelated selenium, ultrafine activated mineral powder, selenate, selenite, selenoamino acid, and selenium-enriched yeast.
4. The method according to claim 1, characterized in that In step 2), the selenium raw material must be dissolved in the solvent at a target dilution multiple according to its water solubility, and the resulting solution or suspension must be able to pass smoothly through the filter screen of the water inlet pipe of the sprayer.
5. The method according to claim 1, characterized in that The liquid storage barrel used in step 3) is a plastic barrel with a capacity of 30-150L and an opening of 10-100 cm. The barrel must include a plastic cover that can be opened and covered to reduce dust from falling into the barrel during the operation.
6. The method according to claim 1, characterized in that In step 4), the platform scale used is an ordinary market weighing flat-bottom scale. The weighing surface of the scale needs to be loose enough to place the liquid bucket. The placement order is: first reset the platform scale reading to zero, then place the liquid bucket, then put the sprayer water inlet pipe into the liquid bucket, and then cover the liquid bucket. After this sequence is completed, the weight reading displayed on the scale is the total weight of "solution + bucket body + bucket cover + water inlet pipe".
7. The method according to claim 1, characterized in that In step 4), the spray rate of the sprayer needs to be calibrated first. The test method is: record the initial reading and time of the scale, record the end reading and time of the scale after spraying for a period of time, calculate the average spray rate of the time period based on the scale reading, and compare the average spray rate with the instantaneous spray rate on the flow meter. If the average spray rate is consistent with the instantaneous spray rate (within the allowable error range), the calibration is completed. If not, the spray rate based on the scale reading must be used as the standard, and the deviation of the flow meter must be calibrated to make it consistent with the spray rate based on the scale.
8. The method according to claim 1, characterized in that In step 6), the amount of solution to be sprayed per unit time is calculated based on the weight of the particles transported per unit time displayed on the belt scale. If the transmission rate of the granular fertilizer on the conveyor belt fluctuates, the solution spraying rate must be adjusted synchronously through the flow control valve according to the changes in the reading on the belt scale, so that the liquid flow meter reading and the belt scale reading are synchronized.
9. The method according to claim 1, characterized in that In step 7), when a barrel of solution is nearly finished, the readings of the platform scale and the belt scale shall be used as the basis, and the total amount of solution sprayed and the total weight of the particles sprayed within the initial and final time interval of the spraying of the barrel of solution shall be counted again. The average selenium content of the particles within the time interval shall be calculated based on the total amount of solution sprayed and the total weight of the granular fertilizer sprayed. If the average selenium content is consistent with the set selenium content, the system is normal. If the average selenium content and the set selenium content exceed the error range, the solution spraying speed shall be slowed down or accelerated according to whether the actual selenium content is too high or too low.
10. The method according to claim 1, characterized in that In step 8), the granular fertilizer sprayed with the selenium solution falls into the drum after passing through the conveyor belt, rotates in the drum to be fully mixed and evenly contacted, and then transferred to the packaging machine for packaging.