Feeding device and control system thereof

Abstract

The invention discloses a feeding device and a control system thereof. The feeding device comprises a sending tank, a high-pressure screw feeder, an air source pipeline and a shunting constant-pressure pipe, wherein the sending tank and the high-pressure screw feeder are communicated through the air source pipeline; the sending tank is provided with a fluidizing pipe and a weighing sensor, the high-pressure screw feeder is driven by a variable frequency motor, an outlet of the high-pressure screw feeder is connected with a discharging pipeline through a dome valve, and multi-group parallel operation can be realized; the pressure transmitter, the adjusting valve and the variable frequency motor are integrally controlled through the PLC, the air pressure and the material state in the tank are monitored and adjusted in real time, the spiral rotating speed is accurately controlled through weighing feedback, continuous, stable and adjustable conveying of powder and particle materials under the high-pressure-difference working condition is achieved, blocking is effectively prevented, and the conveying precision and the system reliability are improved.

Description

Technical Field

[0001] This invention relates to the field of material conveying and process control technology, and in particular to a feeding device and its control system. Background Technology

[0002] In industries such as chemical, metallurgical, energy and environmental protection, it is necessary to stably, continuously and controllably transport powdery materials from storage equipment to downstream reaction or processing units. Existing technologies generally adopt pneumatic conveying combined with mechanical feeding, such as using a sending tank as a temporary storage bin, and using a screw feeder to achieve quantitative output of materials. Such systems usually rely on compressed gas as the conveying medium and control the entry and exit of materials and the start and stop of the system through valve groups.

[0003] The material in the feeding tank of the aforementioned feeding device is prone to bridging or stacking due to moisture, static electricity, or particle characteristics, leading to poor or even interrupted feeding and affecting the continuity of the entire production line. Furthermore, if the air pressure inside the tank is not properly controlled or does not match the inlet pressure of the feeder, it will cause unstable material conveying, resulting in pulse feeding or backflow, affecting the stable operation of downstream processes. At the same time, traditional control methods are relatively crude in adjusting the feeding rate, making it difficult to respond quickly and accurately to the real-time needs of downstream equipment, which can easily lead to oversupply or undersupply of materials. The conveying capacity of a single feeding unit of the aforementioned device is limited. When it is necessary to expand the production capacity, there is a lack of convenient and reliable parallel expansion schemes, and the equipment layout is often bloated. Moreover, after parallel connection, the pressure and flow of each unit interfere with each other, making coordinated control complex.

[0004] Therefore, in response to the problems mentioned above, the present invention proposes a feeding device and its control system. Summary of the Invention

[0005] To overcome the problems of material blockage, poor feeding, unstable conveying pressure, insufficient feeding rate control accuracy, and poor system scalability in existing feeding devices, this invention proposes a feeding device and its control system. This device achieves stable, accurate, and scalable material conveying through a unique pipeline design and multi-parameter closed-loop feedback control.

[0006] The technical solution of the present invention is as follows: a feeding device, including a frame, a feeding tank and a high-pressure screw feeder mounted on the frame, an air source pipeline connecting the high-pressure screw feeder and the feeding tank, a diversion constant pressure pipe connecting the air source pipeline and the lower end of the feeding tank, a feeding valve group installed at the feed inlet of the feeding tank, an outlet dome valve fixedly connected to the high-pressure screw feeder, a discharge pipeline fixedly connected to the other end of the outlet dome valve, a rotary exhaust valve installed at the upper end of the feeding tank, a weighing sensor installed on the frame and the feeding tank, and multiple sets of fluidizing pipes connected to the air source pipeline;

[0007] The feeding device can be connected in parallel in multiple groups. When multiple groups are connected in parallel, the air supply pipelines of multiple feeding devices are connected through a connecting pipe. At the same time, multiple feeding devices share a set of discharge pipelines, and the outlet of the discharge pipeline is connected to the next processing device.

[0008] Preferably, the high-pressure screw feeder includes a feeder housing, a variable frequency motor mounted on the feeder housing, a screw rod fixedly connected to the output shaft of the variable frequency motor via a coupling, and a driven shaft connected to the other end of the screw rod, wherein the feeder housing is provided with a feed inlet, an air inlet, and an air outlet.

[0009] Preferably, the feed inlet is connected to the outlet of the sending tank, the air inlet is connected to one end of the air source pipeline, and the air outlet is connected to the outlet dome valve.

[0010] Preferably, the shunt constant pressure pipe is equipped with a pressure transmitter and a regulating valve for monitoring the pipeline air pressure and adjusting it according to engineering needs.

[0011] Preferably, a check valve is installed on the fluidization pipe to fluidize the biomass pellets in the delivery tank and prevent backflow.

[0012] Preferably, a pressure transmitter and a regulating valve are installed on the discharge pipeline. The discharge pipeline is connected to two branch channels, and each branch channel is equipped with a check valve and an angle seat valve. When a branch channel is blocked, the angle seat valve on that branch channel can be controlled to cut off the branch channel, so that the other branch channel remains unobstructed.

[0013] This invention proposes a control system for a feeding device, comprising: The pressure monitoring unit is used to monitor the internal air pressure of each pipeline via a pressure transmitter. The exhaust control unit is used to control the rotary exhaust valve to open when insufficient material is detected, so as to release the gas pressure in the tank and promote the material to fall, and to control it to close when there is sufficient material. The motor speed control unit is used to control the frequency of the variable frequency motor through the PLC control system, thereby adjusting the rotational speed of the screw and controlling the feeding rate. Each screw space of the screw has the same volume to ensure a constant feeding rate. The PLC control system calculates and sets the rotational speed of the variable frequency motor based on the preset daily conveying capacity range of 100-220 tons, combined with the material weight and screw volume. The air pressure regulating unit is used to maintain the air pressure balance in the delivery tank by adjusting the gas pressure of the air source pipeline and the constant pressure distribution pipe, so as to promote the smooth falling of materials. The fluidization control unit is used to control the injection of high-pressure gas from the fluidization tube to prevent biomass pellets from stacking. It controls the gas pressure in the fluidization tube to be 2-6 MPa. The weighing feedback unit is used to receive the material weight signal collected by the weighing sensor and feed it back to the PLC control system. The PLC control system calculates and controls the speed of the variable frequency motor based on the weighing signal and the preset conveying rate, so as to achieve precise adjustment of the feeding rate. It dynamically adjusts the feeding rate according to the material demand of the downstream gasification tank, and realizes linkage control with the back-end equipment.

[0014] The beneficial effects of this invention are: 1. This invention eliminates the risk of bridging and blockage of powdery materials in the delivery tank through the synergistic effect of the diversion constant pressure tube and multiple sets of fluidizing tubes, and realizes the smooth and stable falling of materials like a fluid. This invention organically combines the uniform distribution of air pressure with local high-pressure pulse disturbance, breaking through the bottleneck of traditional devices that cannot reliably transport adhesive materials by simply relying on gravity or single air force.

[0015] 2. This invention uses a high-pressure screw feeder as a unit that combines pressure locking and volume measurement functions. Combined with a high-precision weighing sensor and PLC closed-loop control, it achieves accurate, continuous and stable control of the conveying rate under high pressure differential conditions. Its control accuracy fluctuation rate can be better than ±2%, which meets the stringent requirements of modern high-end processes such as pressurized gasification for extreme feed stability.

[0016] 3. This invention provides highly modular and intelligent collaborative parallel expansion capabilities. Multiple sets of devices can be conveniently connected in parallel through connecting pipes and a shared discharge pipeline. The control system can automatically balance the load of each unit and achieve seamless switching, solving the problems of difficult expansion and mutual interference during parallel operation of traditional systems, and realizing a linear increase in production capacity. Attached Figure Description

[0017] Figure 1 The diagram shown is a schematic representation of the overall structure of the feeding device of the present invention. Figure 2 The diagram shown is a cross-sectional view of the feeding device of the present invention. Figure 3 The diagram shown is a schematic diagram of the parallel structure of the feeding device of the present invention.

[0018] Explanation of reference numerals in the attached drawings: 1. Feeding tank; 2. High-pressure screw feeder; 3. Air source pipeline; 4. Diverter constant pressure pipeline; 5. First dome valve; 6. Second dome valve; 7. Outlet dome valve; 8. Discharge pipeline; 9. Check valve; 10. Weighing sensor; 11. Rotary exhaust valve; 12. Pressure transmitter; 13. Regulating valve; 14. Connecting pipe; 15. Fluidizing pipe; 16. Manual slide gate valve; 17. Angle seat valve. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 and Figure 2 The present invention provides an embodiment: This invention uses a delivery tank as a buffer and fluidization chamber for materials, a high-pressure screw feeder as a metering and pressure-locking conveying unit, and an air network consisting of an air source pipeline, a diversion constant pressure pipe, and a fluidization pipe as a power and regulation source. It is controlled by a PLC control system to achieve precise management of materials throughout the entire process.

[0021] Open the angle seat valve 17 to connect the feeding system to the sending tank 1. During operation, open the first dome valve 5 and the second dome valve 6. Biomass pellets are loaded into the sending tank 1 through the feeding system above. The bottom of the sending tank 1 is connected to the main gas source pipeline 3 through the diversion constant pressure pipe 4. The gas source pipeline 3 provides a stable high-pressure gas source (compressed air or inert gas), and its pressure can be adjusted within a wide range according to process requirements. One path of high-pressure gas enters the diversion constant pressure pipe 4, forming a uniform lifting and fluidizing air cushion at the bottom of the sending tank 1. The other path enters the casing of the high-pressure screw feeder 2 through the air inlet 205.

[0022] The screw 201 of the high-pressure screw feeder 2 is directly driven by a variable frequency motor 202 via a coupling. Each pitch space of the screw 201 is precision machined to ensure a constant volume. The material in the feeding tank 1 enters the feeder's inlet 204 in a loose state under the action of gravity and the bottom fluidizing air cushion. At this time, the high-pressure gas entering the casing initially mixes with the material. The rotation of the screw 201 pushes the fixed volume of material forward. At the same time, due to the sealing effect of the screw, an effective pressure isolation is formed between the feed inlet and the air outlet 206. The material is forced to the air outlet 206 and fully mixes with the high-pressure gas from the air inlet 205 to form a dense phase material flow with a high solid-to-gas ratio.

[0023] The mixed material flow enters the discharge pipeline 8 through the outlet dome valve 7, and is finally delivered to the downstream gasification tank or reactor. The rotary exhaust valve 11 on the upper part of the sending tank 1 is used to release the pressure inside the tank under specific circumstances (exhausting after initial loading, or during troubleshooting). The weighing sensor 10 installed between the frame and the sending tank monitors the material level in the tank in real time. Key nodes in the entire gas circuit system of this invention, such as the diversion constant pressure pipe 4 and the discharge pipeline 8, are equipped with pressure transmitters 12 and regulating valves 13, forming a pressure monitoring and regulation loop. Multiple sets of fluidizing pipes 15 are set in the cone section of the sending tank, and check valves 9 are installed on them to prevent material backflow. These fluidizing pipes continuously spray high-speed airflow, which can effectively destroy the static or dynamic arches that the material may form, thereby completely solving the bridging and blockage problem.

[0024] Please see Figure 3 When large-scale transportation is required, this invention supports the parallel connection of multiple devices. The air source pipelines 3 of multiple independent units are connected in parallel through the connecting pipe 14 to ensure that the air source pressure of each unit is consistent. The discharge pipelines 8 of each unit are connected to a common main pipe and then connected to downstream equipment. The control system can centrally schedule or independently control the parallel units to realize the expansion of production capacity.

[0025] The control system of this invention constructs a closed-loop control network with PLC as its core. The pressure monitoring unit collects signals from each pressure transmitter 12 in real time, and the weighing feedback unit obtains the material level (weight) signal of the feeding tank. The exhaust control unit controls the rotary exhaust valve 11 to operate before system startup or when it detects that the material in the tank is completely emptied. The air pressure regulation unit ensures that the pressure at the bottom of the feeding tank and inside the screw feeder is within the set range and maintains dynamic balance by controlling the regulating valves 13 on the main air supply pipe and its branches. The fluidization control unit periodically opens the valves on the fluidization pipe 15 according to a preset program or based on the rate of change of the weighing signal (to judge the smoothness of material feeding). The motor speed control unit uses the PLC to calculate the real-time unloading rate (weight reduction per unit time) based on the weighing sensor 10 and compares it with the material demand (set value) from the downstream process. It then dynamically adjusts the speed of the variable frequency motor 202 through algorithms such as PID, thereby accurately controlling the conveying capacity of the screw feeder. The constant volume of the screw space makes the theoretical relationship between the speed and the conveying capacity highly linear.

[0026] This invention provides Embodiment 1: In this embodiment, a set as shown in the attached diagram is configured. Figure 1The single-unit feeding device shown is used to continuously supply pine wood pellets to a biomass gasification furnace. The effective volume of the feeding tank 1 is 10m³. The screw rod 201 of the high-pressure screw feeder 2 has a diameter of 200mm and a pitch of 150mm. The volume of a single screw is approximately 3.5 liters. The air source adopts the factory compressed air pipeline network. After pressure reduction and stabilization, the control system sets the inlet pressure of the air source pipeline 3 to 0.8MPa. The design of the diversion constant pressure pipe 4 stabilizes the bottom pressure of the tank within the range of 0.75-0.78MPa. The injection pressure of the fluidizing pipe 15 is set to 4.0MPa. It adopts a pulse working mode, injecting for 0.5 seconds every 30 seconds.

[0027] The control objective of this embodiment is to ensure that, based on the operating load of the gasifier, the feeding device continuously and stably provides 15 tons (i.e., 250 kg / min) of pine wood pellets per hour, with a conveying volume fluctuation rate not exceeding ±2%.

[0028] Implementation process: Before system startup, the feeding tank was already filled with approximately 5 tons of material. Traditional gravity-feeding methods easily lead to bridging at the bottom outlet of the tank in this type of biomass pellet. After system startup, the uniform air cushion provided by the diversion constant pressure pipe 4 significantly reduced friction between the material and the tank wall. The pulsed fluidizing pipe 15 continuously agitated the material layer. During the entire 72-hour continuous operation test, there were no interruptions or fluctuations in feeding due to poor material flow from the feeding tank. Data from the pressure transmitter 12 showed that the pressure fluctuation range at the bottom of the feeding tank was less than 0.03 MPa, far lower than the >0.1 MPa fluctuations commonly seen in traditional systems, providing extremely stable inlet conditions for the high-pressure screw feeder.

[0029] The PLC control system has a preset target conveying rate of 250 kg / min. Weighing sensor 10 (accuracy 0.1%FS) monitors the tank weight in real time. After the system stabilizes, the PLC collects weight loss data over 10 minutes and calculates the actual average conveying rate to be 248.7 kg / min. Then, based on the preset theoretical screw volume (3.5 L / rev) and material bulk density (approximately 0.65 kg / L), the PLC calculates the target rotational speed as follows:

[0030] The system fine-tunes the frequency of the variable frequency motor 202 to stabilize the speed at 110 rpm, and then performs a weighing feedback correction every 5 minutes. 24-hour statistical data shows that the actual average conveying rate is 249.8 kg / min, the standard deviation is 2.1 kg / min, and the fluctuation rate is ±1.68%, which is lower than the control target of ±2%. This shows that the closed-loop control strategy of the present invention has good effect.

[0031] This invention provides Embodiment 2: This embodiment uses three sets of feeding devices as specified in Embodiment 1, via an attached... Figure 3 The components are connected in parallel as shown, feeding together into a large fluidized bed gasifier, with a total target conveying capacity of 60 tons / hour.

[0032] Implementation results: The gas supply pipelines 3 of the three sets of devices are interconnected through connecting pipes 14, and the pressure is controlled by a main regulating valve 13. The pressure monitoring unit ensures that the pressure at the parallel connection point is consistent, eliminating the imbalance in the delivery of each unit caused by differences in gas supply. During startup, the control system can sequentially start the fluidization, pressurization and feeding programs of each unit to avoid causing a huge instantaneous impact on the gas supply. When a unit needs to be withdrawn for maintenance, its inlet and outlet valves can be closed without affecting the operation of other units, demonstrating good modularity and maintainability.

[0033] The discharge pipelines 8 of the three units converge into a common main pipe, and a pressure transmitter 12 installed on the main pipe monitors the main pipeline pressure. The control system can adopt a master-slave control or average distribution strategy, such as setting all three feeders to operate at a baseline of 20 tons / hour (approximately 333 kg / min). When the weighing feedback shows that the instantaneous output of feeder 1 is slightly lower due to a slight change in material characteristics, the PLC can slightly increase the speed settings of the other two feeders, and at the same time attempt to restore its performance by adjusting the fluidization intensity of feeder 1, ensuring that the total output is stable at 60 tons / hour.

[0034] The dual-branch fault-tolerant design of the discharge pipe 8 in the shared discharge section of the parallel system employs a dual-branch design, with each branch equipped with a check valve 9 and an angle seat valve 17. In simulation testing, artificially closing the angle seat valve 17 of one branch to simulate blockage immediately triggered a pressure increase upstream of that branch. The control system alarmed and, after confirming the blockage, completely shut off the angle seat valve of that branch, switching the entire feed flow to the other branch. The switching process took approximately 2 seconds, with an impact of less than 5% on the feed pressure fluctuation of the downstream gasifier, significantly improving the reliability of continuous system operation.

[0035] This invention provides embodiment 3: This embodiment demonstrates the adaptive capability of the control system in response to different material characteristics. In this example, the processing object is switched from pine wood particles (bulk density 0.65 kg / L, good flowability) to crushed rice husks (bulk density 0.25 kg / L, poor flowability, easy to overlap).

[0036] Implementation process: After switching materials, operators only need to select the "rice husk" formula or enter the bulk density of the new material (0.25 kg / L) on the HMI interface. The control system first executes a self-learning process, running the screw feeder at a low speed under safe pressure, while simultaneously collecting data at high frequency through weighing sensors to quickly establish a model of the correspondence between the rotational speed and the actual conveying capacity under the current material characteristics, correcting for changes in the filling coefficient caused by differences in material flowability.

[0037] For rice husks with poor flowability, the control system automatically increased the workload of the fluidizing tube 15, raising the injection pressure from 4.0 MPa to 5.5 MPa. The pressure monitoring unit showed that the pressure fluctuation at the bottom of the delivery tank was slightly greater than when processing pine wood, but it was still kept within the allowable range thanks to the rapid response of the air pressure regulating unit.

[0038] The target conveying capacity is set at 10 tons / hour (approximately 166.7 kg / min). After correction using the self-learning model, the PLC calculates a new theoretical rotational speed of approximately: ; After the system was running stably, the measured average conveying rate was 165.3 kg / min with a fluctuation rate of ±2.5%. Although this was slightly less accurate than when processing pine wood, traditional systems often had fluctuation rates exceeding ±10% or even experienced material shortages for materials with such poor flowability.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A feeding device, comprising a frame, characterized in that: It includes a feeding tank (1) and a high-pressure screw feeder (2) installed on the frame, an air supply pipeline (3) connecting the high-pressure screw feeder (2) and the feeding tank (1), a shunt constant pressure pipe (4) connecting the air supply pipeline (3) and the lower end of the feeding tank (1), a feed valve group installed at the feed inlet of the feeding tank (1), an outlet dome valve (7) fixedly connected to the high-pressure screw feeder (2), a discharge pipeline (8) fixedly connected to the other end of the outlet dome valve (7), a rotary exhaust valve (11) installed at the upper end of the feeding tank (1), a weighing sensor (10) installed on the frame and the feeding tank (1), and multiple fluidizing pipes (15) connected to the air supply pipeline (3). The feeding device can be connected in parallel in multiple groups. When multiple groups are connected in parallel, the air supply pipelines (3) of multiple feeding devices are connected through the connecting pipe (14). At the same time, multiple feeding devices share a set of discharge pipelines (8). The outlet of the discharge pipeline (8) is connected to the next processing device. The feed valve assembly includes a first dome valve (5) installed at the inlet of the feeding tank (1), a second dome valve (6) connected to the first dome valve (5) via a flexible joint, and a manual slide valve (16) installed on the second dome valve (6).

2. The feeding device according to claim 1, characterized in that: The high-pressure screw feeder (2) includes a feeder housing, a variable frequency motor (202) mounted on the feeder housing, a screw rod (201) fixed to the output shaft of the variable frequency motor (202) via a coupling, and a driven shaft (203) connected to the other end of the screw rod (201). The feeder housing is provided with a feed inlet (204), an air inlet (205), and an air outlet (206).

3. The feeding device according to claim 1, characterized in that: The feed inlet (204) is connected to the outlet of the sending tank (1), the air inlet (205) is connected to one end of the air source pipeline (3), and the air outlet (206) is connected to the outlet dome valve (7).

4. The feeding device according to claim 1, characterized in that: The pressure transmitter (12) and regulating valve (13) are installed on the shunt constant pressure pipe (4) to monitor the pipeline air pressure and adjust it according to the engineering needs.

5. A feeding device according to claim 1, characterized in that: A check valve (9) is installed on the fluidization pipe (15) to fluidize the biomass particles in the fluidization tank (1) and prevent backflow.

6. A feeding device according to claim 1, characterized in that: The discharge pipeline (8) is equipped with a pressure transmitter (12) and a regulating valve (13). The discharge pipeline (8) is connected to two branch channels. Each branch channel is equipped with a check valve (9) and an angle seat valve (17). When a branch channel is blocked, the branch channel can be cut off by controlling the angle seat valve (17) on that branch channel, so that the other branch channel remains unobstructed.

7. A control system for a feeding device, controlling the feeding device according to any one of claims 1-6, characterized in that, Including: The pressure monitoring unit is used to monitor the internal air pressure of each pipeline through the pressure transmitter (12); The exhaust control unit is used to control the rotary exhaust valve (11) to open when insufficient material is detected to release the gas pressure in the tank and promote the material to fall, and to control it to close when there is sufficient material. The motor speed control unit is used to control the frequency of the variable frequency motor (202) through the PLC control system, thereby adjusting the speed of the screw (201) and controlling the feeding rate. The air pressure regulating unit is used to maintain the air pressure balance in the sending tank (1) by regulating the gas pressure of the air source pipeline (3) and the diversion constant pressure pipe (4), so as to promote the smooth falling of materials; Fluidization control unit, used to control the injection of high-pressure gas from fluidization tube (15) to prevent biomass pellets from stacking; The weighing feedback unit is used to receive the material weight signal collected by the weighing sensor (10) and feed it back to the PLC control system; The PLC control system calculates and controls the rotational speed of the variable frequency motor (202) based on the weighing signal and the preset conveying rate, thereby achieving precise adjustment of the feeding rate.

8. The control system of the feeding device according to claim 7, characterized in that: The fluidization control unit controls the gas pressure in the fluidization tube (15) to be 2-6 MPa.

9. The control system of the feeding device according to claim 7, characterized in that: Each spiral space of the screw rod (201) has the same volume, ensuring a constant feeding rate; the PLC control system calculates and sets the speed of the variable frequency motor (202) based on the preset daily conveying capacity range of 100-220 tons, combined with the material weight and the spiral volume.

10. The control system of the feeding device according to claim 7, characterized in that: The PLC control system is also used to dynamically adjust the feeding rate according to the material requirements of the downstream gasification tank, so as to realize the linkage control with the back-end equipment.

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