A vacuum pipeline conveying system for easily hygroscopic bulk materials

Abstract

This utility model discloses a vacuum pipeline conveying system for easily hygroscopic bulk materials, belonging to the field of environmental protection equipment technology. This utility model consists of an air dryer unit, a drying air sealing device, a low-level hopper, a pipeline air replenishment device, a vacuum conveying pipeline, a vacuum feeder, a negative pressure device, and an air compressor unit. It reduces the relative humidity of the air in contact with the easily hygroscopic bulk materials and adjusts the air temperature to a level where the materials are less likely to absorb moisture. Using a vacuum pipeline closed-loop conveying process, the material is transported to downstream equipment. This solves the problems of difficult transport and transfer of easily hygroscopic bulk materials in actual production, as well as the high cost of other vacuum pipeline conveying methods. It achieves vacuum pipeline closed-loop conveying of such materials, effectively controlling dust hazards to the health of production personnel and the environment, effectively reducing production costs, and facilitating market adoption.

Description

Technical Field

[0001] This utility model relates to the field of environmental protection equipment technology, and in particular to the field of vacuum pipeline conveying systems for easily hygroscopic bulk materials. Background Technology

[0002] Moisture-absorbing bulk materials are commonly used in the chemical, food, pharmaceutical, and biotechnology industries. Currently, in actual production processes, these materials readily absorb moisture upon contact with natural air. Moisture absorption directly affects product quality and material properties, and it adheres to pipes and equipment, causing blockages and preventing vacuum pipeline transportation. Current traditional and existing production processes in my country for these materials employ the following methods: 1. Using nitrogen-protected vacuum pipeline transportation; 2. Drying the material before vacuum pipeline transportation; 3. Using manual and mechanical feeding and transfer. The nitrogen-protected vacuum pipeline conveying process is only suitable for low-volume operations because nitrogen costs are high, especially at higher volumes where hourly nitrogen consumption can reach hundreds or even thousands of cubic meters. Even with nitrogen recovery, significant investment in nitrogen generation equipment and energy consumption is required, making it unaffordable for production enterprises. Drying materials before conveying can negatively impact the quality and properties of materials that cannot be dried, and this method consumes substantial amounts of energy at high volumes. Manual and mechanical feeding and transfer processes generate dust, harming human health and the environment. Therefore, we have designed a lower-cost vacuum pipeline conveying system and process for hygroscopic bulk materials. This system isolates hygroscopic bulk materials from relatively humid air, enabling closed-loop pipeline conveying and transfer. It also allows for vacuum pipeline conveying of materials where increased dryness is not advisable. This will positively impact personnel health, environmental protection, and effectively reduce energy consumption and costs.

[0003] Chinese patent CN214308088U discloses an integrated powder feeding and drying equipment, specifically relating to the field of conveying equipment manufacturing. It includes a vacuum feeder, an air-source heat pump circulating dryer, and a powder storage tank, connected in series. This invention allows powder to maintain and increase its dryness even when fed and transported in humid environments. By adjusting the temperature and dryness of the airflow output from the air-source heat pump circulating dryer, the pre-drying process can even be eliminated, completing feeding and drying in one step during powder feeding and transport, thus simplifying the production process and improving efficiency. This solution integrates feeding and drying, conveying materials while increasing their dryness. However, this process can affect the quality and properties of certain materials that cannot be dried. When the conveying volume is large, such as 10-30 tons / hour, achieving both material drying and conveying requires significant energy consumption. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies such as easy blockage of pipelines and equipment by hygroscopic bulk materials, high production cost of nitrogen protection process, characteristic effects of integrated feeding and drying process on materials that are not suitable for drying, and dust generation caused by manual and mechanical conveying.

[0005] In view of at least one of the above technical problems, this utility model provides a vacuum pipeline conveying system for easily hygroscopic bulk materials, solving the problems of the difficulty and high cost of conveying easily hygroscopic bulk materials using vacuum pipelines, effectively controlling dust and reducing production costs. The specific technical solution is as follows: A vacuum pipeline conveying system for easily hygroscopic bulk materials includes a feeding device, an air dryer unit, a drying air sealing device, a low-level hopper, a pipeline air replenishment device, a vacuum conveying pipeline, a vacuum feeder, a negative pressure device, and an air compressor unit. The air dryer is located outside the air drying enclosure, and an air drying input channel is connected between the air dryer and the air drying enclosure. The dry air sealing device is a closed shell, its function being to partially seal off parts of the system that require air intake, isolating them from ambient air. This device can either completely seal off equipment where air enters, or partially seal off parts of equipment where air enters. A feeding device is installed on the dry air sealing device; this feeding device is a bulk material production device outside this vacuum pipeline conveying system. The feeding device is an upstream device that feeds material into the low-level hopper. The feeding device has a closed shell, its upper part located outside the dry air sealing device. The upper part of the feeding device has a sealable feeding port, and a dry air inlet pipe serves as a dry air input channel between the upper part of the feeding device and the dry air sealing device. The feeding device can be a mixer, with its lower part connected to the feed inlet at the upper part of the low-level hopper via a rotary unloader.

[0006] The low-level hopper, the lower part of the feeding equipment, and the pipeline air supply device are all located inside the dry air sealing device. Their process feature and purpose is to inject dry air into the low-level hopper, the pipeline air supply device, and the upper part of the feeding equipment to isolate the material from the humid air. The lower part of the feeding equipment is connected to the feed inlet at the top of the low-level hopper via a discharge device. The discharge outlet of the low-level hopper is connected to the pipeline air supply device, which is connected to a vacuum conveying pipeline. The vacuum conveying pipeline extends outside the dry air sealing device and connects to the vacuum feeder. The vacuum feeder is connected to the negative pressure equipment and the air compressor unit.

[0007] As one embodiment of this disclosure, the low-level hopper includes a hopper body, which is a bucket-shaped hopper that is larger at the top and smaller at the bottom. The hopper body is provided with a sealing cover, an air inlet and a feed inlet, and a support leg at the bottom of the hopper body. The discharge outlet is provided at the bottom of the hopper body.

[0008] As one embodiment of this disclosure, the pipeline air replenishment device is installed at the connection between the low-level hopper and the vacuum conveying pipeline. The pipeline air replenishment device includes two pipeline tees, and the two pipeline tees are connected to a pipeline shut-off valve through a connecting flange. The pipeline tees at the front end of the pipeline air replenishment device are provided with an air replenishment port air filter, and the pipeline tees at the rear end of the pipeline air replenishment device are provided with an air inlet air filter and a pipeline emptying valve.

[0009] As one embodiment of this disclosure, the feeding equipment is a bulk material production equipment outside this system, and is an upstream equipment of this system, including mixers, feeding stations, dryers and other bulk material production equipment that can feed materials into low-level hoppers.

[0010] As one embodiment of this disclosure, the air pressure inside the dry air sealing device is a slightly positive pressure greater than standard atmospheric pressure, and the air flow rate entering the dry air sealing device is greater than the air flow rate pumped out by the vacuum pipe.

[0011] Compared with existing technologies, our vacuum pipeline conveying system and process for easily hygroscopic bulk materials have the following advantages: 1. This utility model is effective for vacuum pipeline conveying of easily hygroscopic bulk materials with large production volumes (especially 10-30 tons / hour), and has relatively high energy efficiency. It is designed for production enterprises in intermediate production stages involving easily hygroscopic bulk materials, transporting such materials from upstream equipment to downstream equipment via this system. To achieve this function, it consists of an air dryer unit, a drying air sealing device, a low-level hopper, a pipeline air replenishment device, a vacuum conveying pipeline, a vacuum feeder, a negative pressure device, an air compressor unit, and a control unit. Through the coordinated work of the air dryer unit, drying air sealing device, low-level hopper, pipeline air replenishment device, vacuum conveying pipeline, vacuum feeder, negative pressure device, air compressor unit, and control unit, the relative humidity of the air in contact with the easily hygroscopic bulk materials is reduced, and the air temperature is adjusted to a temperature where the material is less likely to absorb moisture. Using a vacuum pipeline closed conveying process, the material is transported to the downstream equipment, solving the problems of the difficulty in using vacuum pipeline conveying of easily hygroscopic bulk materials and the high cost of other vacuum pipeline conveying processes, thus achieving vacuum pipeline closed conveying of such materials. Compared with existing patents, this utility model does not dry the material but only the air, which can be transported without increasing the dryness of the material, and its energy efficiency is better than that of existing patents when the production volume is large.

[0012] 2. This utility model effectively controls the dust generated by such materials during the production process, which is harmful to the health of production personnel and the environment, and is energy-saving and environmentally friendly.

[0013] 3. This utility model can achieve vacuum pipeline closed transport of such materials without nitrogen protection, which greatly reduces production costs, equipment costs and maintenance costs, and facilitates market adoption.

[0014] 4. This utility model can transport materials through vacuum pipelines without increasing the dryness of the materials, thus effectively maintaining the original characteristics of the materials. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram showing the flow direction of the dry air inlet pipeline replenishment device of this utility model; Figure 3 This is a schematic diagram of the system structure and production process of this utility model; Figure 4 This is a schematic diagram of the low-level hopper structure of this utility model; Figure 5 This is a schematic diagram of the pipeline gas supply device of this utility model; Figure 6 This is a table showing the power consumption of equipment in a real-world production case.

[0016] In the diagram, 1. Air drying unit; 2. Drying air sealing device; 2-1. Positive pressure relief valve; 2-2. Drying air inlet pipe; 3. Low-level hopper; 3-1. Air inlet; 3-2. Sealing cover; 3-3. Support leg; 3-4. Discharge port; 3-5. Storage hopper body; 3-6. Feed inlet; 4. Pipeline air replenishment device; 4-1. Pipeline purging valve; 4-2. Air inlet air filter; 4-3. Air replenishment port air filter; 4-4. Pipeline tee; 4-5. Connecting... 4-6. Connecting flange; 4-7. Quick-connect clamp; 4-8. Filter element; 4-9. Filter housing; 4-1. Pipeline shut-off valve; 5. Vacuum conveying pipeline; 6. Vacuum feeder; 7. Air compressor unit; 8. Negative pressure equipment; 9. Negative pressure pipeline; 10. Rotary unloader; 11. Packaging machine; 12. Roots blower; 13. Control unit; 14. Mixer; 14-1. Air inlet filter; 14-2. Inspection hole; 15. Compressed air pipe; 16. Rotary unloader. Detailed Implementation

[0017] To better understand the purpose, structure, and function of this utility model, the technical solutions in the embodiments of this utility model will be clearly and completely described below.

[0018] It should be noted that, 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The terms "comprising" and "having" and any variations thereof, as used herein, are open-ended and intended to cover non-exclusive inclusion.

[0019] The component numbers used in this document are solely for distinguishing the objects described and have no sequential or technical meaning. Unless otherwise specified, the term "connection" in this disclosure includes both direct and indirect connections.

[0020] It should be understood that the hygroscopic bulk materials in this application refer to hygroscopic powders or granular materials, for example: 1. Calcium chloride: Colorless, white, or grayish-white cubic crystals or powder, highly hygroscopic. Its deliquescence point is usually at room temperature (25℃) and relative humidity of 30%. That is, it can absorb moisture in environments with relative humidity greater than 30%, and the material properties will decrease or even be damaged after absorbing moisture.

[0021] 2. Sodium citrate: colorless transparent crystals or white crystalline powder. When the relative humidity of the air is greater than 70%, it easily absorbs moisture from the air and deliquesces, gradually changing from solid particles to a moist state, and may even partially dissolve to form a liquid; however, if it is not dried properly, it will melt and clump together.

[0022] 3. Anhydrous magnesium chloride: White, lustrous hexagonal crystals. Its deliquescence point is typically around 33% relative humidity at room temperature (25℃). It absorbs moisture when the relative humidity is greater than 33%, which degrades its properties and can even damage it.

[0023] The above are merely examples to facilitate clear understanding by those skilled in the art, and are not intended to limit the scope of protection of this application.

[0024] As shown in the attached diagram. Figures 1 to 5 As shown, a vacuum pipeline conveying system for easily hygroscopic bulk materials includes a feeding device, an air dryer unit 1, a drying air sealing device 2, a low-level hopper 3, a pipeline air replenishment device 4, a vacuum conveying pipeline 5, a vacuum feeder 6, an air compressor unit 7, a negative pressure device 8, and a control unit 13.

[0025] like Figure 3 As shown, the dry air sealing device 2 is a closed shell. The feeding device is installed on the upper part of the dry air sealing device 2. The feeding device is the upstream device for feeding material into the low-level hopper 3. The feeding device is a bulk material production device outside this system and is the upstream device of this system. The upper part of the feeding device is located outside the dry air sealing device 2. The upper part of the feeding device is provided with a sealable feeding port. A dry air input channel, such as a dry air inlet pipe 2-2, is provided between the upper part of the feeding device and the dry air sealing device 2. Its function is to supplement dry air into the feeding device when the material is discharged from the feeding device.

[0026] The air dryer unit 1 is located outside the air drying enclosure 2, and an air drying input channel is connected between the air dryer unit 1 and the air drying enclosure 2.

[0027] The low-level hopper 3 is located inside the dry air sealing device 2. The lower part of the feeding device is located inside the dry air sealing device and is connected to the feed inlet 3-6 at the upper part of the low-level hopper 2 through the unloader. The discharge port 3-4 of the low-level hopper 3 is connected to the pipeline air supply device 4. The pipeline air supply device 4 is connected to the vacuum conveying pipeline 5. The vacuum conveying pipeline 5 extends out of the dry air sealing device 2 and is connected to the vacuum feeder 6. The vacuum feeder 6 is connected to the negative pressure device 8 and the air compressor unit 7.

[0028] As one embodiment of this disclosure, such as Figure 3 , Figure 4As shown, the low-level hopper 3 includes a hopper body 3-5, which is a bucket-shaped hopper that is larger at the top and smaller at the bottom. The hopper body 3-5 is provided with a sealing cover 3-2, an air inlet 3-1 and a feed inlet 3-6. The hopper body 3-5 is provided with support legs 3-3 at the bottom. The air inlet 3-1 is equipped with an air filter, which functions to prevent dust from overflowing and to replenish dry air into the hopper when the material is discharged. The hopper body 3-5 is provided with a discharge outlet 3-4 at the bottom.

[0029] As one embodiment of this disclosure, such as Figure 3 , Figure 5 As shown, the pipeline air replenishment device 4 is installed at the connection between the low-level hopper 3 and the vacuum conveying pipeline 5. The pipeline air replenishment device 4 includes two pipeline tees 4-4, which are connected to a pipeline shut-off valve 4-9 via a connecting flange 4-5. An air replenishment port air filter 4-3 is installed on the pipeline tees 4-4 at the front end of the pipeline air replenishment device 4, and an air inlet air filter 4-2 and a pipeline emptying valve 4-1 are installed on the pipeline tees 4-4 at the rear end of the pipeline air replenishment device 4. Both the air replenishment port air filter 4-3 and the air inlet air filter 4-2 include a quick-release clamp 4-6, a filter element 4-7, and a filter housing 4-8. The function of the pipeline air replenishment device is: when conveying materials, the device installed at the front end replenishes dry air into the pipeline; when the material conveying ends, the main pipeline shut-off valve closes, and the pipeline emptying valve opens to allow dry air to enter and empty the pipeline.

[0030] As one embodiment of this disclosure, the feeding equipment is a bulk material production device outside this system, and is an upstream device of this system, including a mixer, feeding station, dryer, or other bulk material production equipment that can feed materials into a low-level hopper. Figure 3 The feeding device shown is a mixer 14. The upper part of the mixer 14 includes an air inlet filter 14-1 and an inspection hole 14-2. The lower part of the mixer 14 is connected to the feed port of the upper part of the low-level hopper 3 through a rotary unloader 16.

[0031] As one embodiment of this disclosure, the air pressure inside the dry air sealing device 2 is a slightly positive pressure that is slightly greater than the standard atmospheric pressure. Here, the slightly positive pressure is generally an air pressure that exceeds the standard atmospheric pressure by 5%-10%. If it is slightly exceeded according to the actual situation, those skilled in the art will understand. The air flow rate entering the dry air sealing device is greater than the air flow rate pumped out by the vacuum pipe. The dry air sealing device 2 is equipped with a positive pressure relief valve 2-1.

[0032] This invention discloses a vacuum pipeline conveying process for easily hygroscopic bulk materials. The system utilizes an air dryer to input dried and temperature-controlled air into a drying air sealing device, which isolates the material from the humid air during material transport. After material arrives at the upstream feeding equipment, it enters the low-level hopper and is then drawn away by the negative pressure within the vacuum pipeline connected to the bottom of the hopper. Simultaneously, dry air enters the upstream equipment, the low-level hopper, and the pipeline air replenishment device. The material is then pumped to a vacuum feeder and discharged into the downstream equipment.

[0033] The process of dry air in the system: Air from nature that is above the deliquescence point of the material and whose temperature is unsuitable is dried and temperature controlled by the air dryer unit and then input into the dry air sealing device. It then enters the upstream equipment, the low-level hopper, the pipeline air replenishment device, and the vacuum conveying pipeline. It enters the vacuum feeder through the vacuum conveying pipeline and finally enters the downstream equipment, thus completing the process of isolating the easily hygroscopic bulk materials from the humid air.

[0034] The process of hygroscopic bulk materials in this system is as follows: The hygroscopic bulk materials enter the low-level hopper through the upstream equipment, pass through the pipeline air replenishment device, the vacuum conveying pipeline, the vacuum feeder, and are discharged into the downstream equipment, thus completing the vacuum pipeline conveying process of the hygroscopic bulk materials.

[0035] As one embodiment of this disclosure, the overall material conveying process system is centrally controlled by the control unit, i.e., the control management module, which is equipped with an intelligent PLC central processing unit (CPU) and uses DCS bus communication to achieve centralized monitoring and management with other production equipment.

[0036] Further explanation: The bulk material is in powder form (particle size 5nm-100μm) or granular form (particle size 100μm-30mm).

[0037] The humid air is air with a relative humidity higher than the deliquescence point of easily hygroscopic bulk materials.

[0038] The dry air is air with a relative humidity lower than the deliquescence point of easily hygroscopic bulk materials.

[0039] The air dryer unit is an air drying and temperature control device. Its purpose is to dry air with a relative humidity higher than the material's deliquescence point to air with a relative humidity lower than the material's deliquescence point, and to control the temperature to meet the process requirements of this system. Air dryers can be selected from products such as XSFLHS-55-WT and XSFLHS-20-WT manufactured by Shanghai Xieshou Environmental Technology Co., Ltd.

[0040] The dry air sealing device is a device that seals off a local space. Its purpose is to seal off the local space so that dried and temperature-controlled air can enter the material conveying system, thus isolating the relatively humid air from the material.

[0041] The low-level hopper is a cone-shaped hopper that is larger at the top and smaller at the bottom. Its function is to collect and buffer the material discharged from the upstream equipment, so that the material can smoothly enter the vacuum conveying pipeline. The upstream equipment refers to the production equipment for other bulk materials, which is equipment that feeds materials into this system, but is not part of the equipment in this system.

[0042] The downstream equipment is the final deployment point of this system, but it is not part of the equipment in this system.

[0043] The pipeline air supply device is a device that supplies dry air into the pipeline when materials are transported through it.

[0044] The vacuum conveying pipeline is a device for conveying materials in a closed system.

[0045] The vacuum feeder is a device that uses vacuum negative pressure to transport bulk materials through pipelines. It consists of a filter element, a back-flushing dust removal device, a machine chamber, a feed control valve, a vacuum control valve, a discharge control valve, a vibrating device, pneumatic components, and a control unit. Its automatic mechanical actions are completed by a control management module. Vacuum feeders can be selected from models manufactured by Xuzhou Zhengsheng Environmental Protection Equipment Manufacturing Plant, such as ZS-SLJ-320, ZS-SLJ-600, and ZS-SLJ-1000.

[0046] The negative pressure equipment in this system serves as a device to provide vacuum negative pressure power for the material conveying and flow within the system. Depending on the specific operating conditions, the negative pressure equipment can be selected from components such as Roots blowers, rotary vane vacuum pumps, and water ring vacuum pumps.

[0047] The air compressor unit in this system is used to provide compressed air to the backflushing dust removal and pneumatic component units in the system, and to dry the compressed air.

[0048] The Control Management Module (CMM) is equipped with an intelligent PLC central processing unit (CPU) and uses DCS bus communication to achieve compatibility with other equipment for centralized monitoring and management. The CMM's function in this system is to automatically control the automatic mechanical actions, parameters, and operating condition alarms throughout the system, and to manage, coordinate, and monitor all process functions. The CMM and other electrical components are installed inside and on the surface of the automatic control cabinet. The operating interface uses a button + touchscreen mode. A process flow diagram is used to facilitate the operation and adjustment of parameters and actions within the system. Its operational logic in this system is as follows: Air with relatively high humidity from the natural environment is dried and temperature-controlled by an air dryer unit, and then fed into a closed-loop drying air device by a fan. This closed-loop drying air device is equipped with a low-level hopper and a pipeline air supply device. Simultaneously, hygroscopic materials transported from upstream equipment also enter the closed-loop drying air device, where they are fed into the low-level hopper. The bottom of the low-level hopper has an outlet connected to a vacuum conveying pipeline. The supplementary air required for vacuum negative pressure conveying of materials enters through the low-level hopper and the pipeline air supply device; all air entering the system is dry air from a sealed space. After the material is drawn away by the negative pressure in the vacuum pipeline, it enters the vacuum feeder, which then feeds the material to downstream equipment, thus completing the automated control process of the entire system. Simultaneously, the control management module also controls the negative pressure equipment that provides negative pressure to the system. The air compressor unit is autonomously controlled and is not part of this system's control.

[0049] Examples of actual production cases: Technical requirements: Under conditions of 85% relative humidity and 32℃, the material containing calcium chloride powder, after being mixed in a mixer, shall be conveyed to the packaging machine 11 via vacuum pipeline. The conveying capacity is 12 tons / hour, the conveying height is 12 meters, and the horizontal conveying distance is 50 meters. Material characteristics: bulk density 0.7 tons / cubic meter, powdery, it will absorb moisture when the air humidity is >30%. During production, the relative humidity of the air in contact with the material must be controlled at 26% (±1%), and the air temperature must be controlled at 26℃ (±2℃). To meet this technical requirement, the main equipment and production technical parameters of the system are as follows: Air dryer unit 1, model XSFLHS-55-WT, dries outdoor air to a relative humidity of 27%, controls the temperature of the dried air to 25℃, has a flow rate of 2500 cubic meters per hour, and a wind pressure that is 5%-10% higher than the standard atmospheric pressure inside the air drying enclosure. Roots blower 12, model DCY-150, air pressure -45Kpa, air volume 2280 cubic meters / hour; Vacuum feeder 6, model ZS-SLJ-1200, conveying capacity 12 tons / hour; Final production result: After the material is conveyed to the packaging machine by this system and packaged, it is placed in an environment with a relative humidity of 75%-90% and an air temperature of 25℃-34℃ for 15 days. The material does not absorb moisture, clump, or become sticky, thus meeting the production technical requirements.

[0050] Actual production case study equipment power consumption table (per ton of material conveyed), see Figure 6 .

[0051] In summary, the technology in this application uses electricity to dry air, while Chinese patent CN214308088U uses electricity to dry materials. Under the same power conditions, drying air is significantly faster than drying materials, making the system in this application more energy-efficient. Furthermore, this application is a vacuum pipeline conveying system for easily hygroscopic bulk materials, drying only the air and not the materials themselves. This is particularly energy-saving for high-volume production operations, allowing for vacuum pipeline conveying of materials where increased dryness is not advisable. Chinese patent CN214308088U, on the other hand, describes a powder feeding and drying integrated equipment system that improves material dryness through pipeline conveying, but it does not mention whether it can convey granular (e.g., particle size 3-30mm) bulk materials. Therefore, its process system differs significantly from this application in both technology and process.

[0052] It is understood that the above description is only for illustrating specific implementation methods of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions based on the technical scope disclosed in this application should be covered within the scope of disclosure of this application.

Claims

1. A vacuum pipeline system for the transport of a hygroscopic bulk material, characterized in that: This includes air drying units, dry air sealing devices, low-level hoppers, pipeline air supply devices, vacuum conveying pipelines, vacuum feeders, negative pressure equipment, and air compressor units; The air dryer is located outside the air drying enclosure, and an air drying input channel is connected between the air dryer and the air drying enclosure. The air-drying device is a closed shell, and a feeding device is installed on it. The low-level hopper is located inside the air-drying device, and the lower part of the feeding device is located inside the air-drying device and connected to the feed inlet at the top of the low-level hopper. The discharge outlet of the low-level hopper is connected to a vacuum conveying pipe. The vacuum conveying pipe inside the air-drying device is equipped with a pipe air replenishment device. The vacuum conveying pipe extends out of the air-drying device and connects to the vacuum feeder. The vacuum feeder is connected to the negative pressure device and an air compressor unit.

2. The vacuum pipeline conveying system for easily hygroscopic bulk materials according to claim 1, characterized in that, The low-level hopper includes a hopper body, which is a bucket-shaped hopper that is larger at the top and smaller at the bottom. The hopper body is equipped with a sealing cover, an air inlet and a feed inlet. The hopper body is equipped with support legs at the bottom and a discharge outlet at the bottom.

3. The vacuum pipeline conveying system for easily hygroscopic bulk materials according to claim 1, characterized in that, The pipeline air replenishment device is installed at the connection between the low-level hopper and the vacuum conveying pipeline. The pipeline air replenishment device includes two pipeline tees, and the two pipeline tees are connected to a pipeline shut-off valve through a connecting flange. The pipeline tees at the front end of the pipeline air replenishment device are equipped with air inlet air filters, and the pipeline tees at the rear end of the pipeline air replenishment device are equipped with air inlet air filters and pipeline emptying valves.

4. The vacuum pipeline conveying system for easily hygroscopic bulk materials according to claim 1, characterized in that, The feeding device is a bulk material production device outside this vacuum pipeline conveying system. The feeding device is an upstream device that feeds material into the low-level hopper. The feeding device has a closed shell. The upper part of the feeding device is located outside the dry air sealing device. The upper part of the feeding device is provided with a sealable feeding port. A dry air inlet pipe is provided between the upper part of the feeding device and the dry air sealing device.

5. The vacuum pipeline conveying system for easily hygroscopic bulk materials according to claim 1 or 4, characterized in that, The feeding device is a mixer, and the lower part of the mixer is connected to the feed inlet at the top of the low-level hopper via a rotary unloader.

6. The vacuum pipeline conveying system of hygroscopic bulk material according to claim 1, characterized in that The pressure inside the dry air sealing device is a slightly positive pressure greater than standard atmospheric pressure, and the air flow rate entering the dry air sealing device is greater than the air flow rate pumped out by the vacuum pipe.

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