A concrete mixing plant ton bag powder feeding control system

Abstract

This invention provides a feeding control system for ton bags of powder in a concrete mixing plant. In the field of feeding control technology, it proposes a vertical lifting method to replace horizontal pneumatic conveying, and gravity unloading to replace mechanical airlock feeding. By hoisting the entire ton bag to the top of the silo and directly unloading it by gravity, it completely eliminates the high-speed wear and tear and airlock requirements in the powder conveying process, achieving a significant simplification of the process and a qualitative leap in reliability. The system's continuous feeding capacity is greatly improved compared to existing technologies, completely solving the supply bottleneck. Dust concentration in the working area is reduced, eliminating dust pollution caused by leakage from the rotary unloading valve at the source, significantly improving the working environment. The expected lifespan of the bag breaker is longer than that of existing rotary unloading valves. The economic benefits are extremely outstanding.

Description

Technical Field

[0001] This invention relates to the field of material feeding control technology, specifically to a material feeding control system for ton bags of powder in a concrete mixing plant. Background Technology

[0002] With the rise of infrastructure construction in emerging global markets, concrete mixing plants, as an indispensable base for engineering construction, are rapidly expanding their footprint to remote peninsulas, islands, and inaccessible land areas in Southeast Asia, Africa, and the South Pacific. In these regions, limited by weak road networks, insufficient bridge load-bearing capacity, or lack of land access, conventional bulk cement trucks with a load capacity of tens of tons cannot reach these areas. This forces mixing plants to abandon the efficient and economical bulk cement supply model and instead adopt 1- to 1.5-ton bagged cement as their main material source. All building materials rely on sea freight to simple docks, followed by short-distance vehicle transport. The supply of powder materials is entirely dependent on ton-bag cement, constituting a fundamental constraint that project construction must face.

[0003] Traditional concrete mixing plants' powder feeding systems are designed specifically for bulk cement tanker trucks and generally employ mature pneumatic conveying technology. However, when dealing with ton bag packaging, existing market solutions often involve a simple approach of connecting the pneumatic conveying system after the unpacking process. The FQS-20 ton bag unpacking machine system initially purchased for this mixing plant project is designed to use the negative pressure generated by a Roots blower for suction conveying, with a theoretical capacity of 20t / h. However, after actual operation, the system's efficiency declined rapidly, and core components such as the conveying pipelines and rotary discharge valves experienced abnormally severe wear, requiring frequent maintenance and replacement. This not only directly increased operating costs but also severely impacted the continuity and stability of production due to frequent downtime caused by malfunctions.

[0004] Therefore, improvements are needed to overcome the aforementioned defects and ensure that the supply of powder materials meets the requirements of continuous production. This is crucial for ensuring the timely progress of overseas engineering projects and controlling costs. It is also essential to fundamentally solve the problem of short lifespan of vulnerable parts, significantly reduce spare parts consumption and downtime losses, and improve the overall economic benefits and competitiveness of projects in harsh environments. Furthermore, it is necessary to control dust generation and dispersion from the design stage, reduce dust concentration in workplaces, improve workers' working conditions, and comply with internationally accepted occupational health and safety standards and green construction concepts. Summary of the Invention

[0005] In order to overcome the problems in the prior art, the present invention provides a feeding control system for ton bag powder materials in a concrete mixing plant.

[0006] The present invention employs the following technical solution.

[0007] A feeding control system for ton bag powder materials in a concrete mixing plant, comprising:

[0008] An electric hoist is installed on the outside of the side wall of the powder silo in a concrete mixing plant.

[0009] An opening is provided at the top of the powder silo in the concrete mixing plant.

[0010] A grid made of welded steel sections is installed above the opening to hold the ton bags and guide them to fall onto the bag breaker.

[0011] A bag-breaking device with a four-sided pyramidal structure;

[0012] A dustproof sealing system installed next to the opening;

[0013] The electrical control system that connects to the motor of the wire rope electric hoist.

[0014] Preferably, the I-beam running track of the electric hoist is fixed to the bracket support pre-welded to the side wall of the powder silo of the concrete mixing plant by high-strength bolts;

[0015] The electric hoist is located on the top working platform of the powder silo in the concrete mixing plant. It can vertically lift the ton bags from the ground to the top of the bag breaker in the powder silo of the concrete mixing plant for unloading.

[0016] The H-beam running track is directly aligned with the center of the unloading opening at the top of the powder silo of the concrete mixing plant.

[0017] Preferably, the selection and design of the electric hoist includes:

[0018] Determine the design rated lifting capacity, which includes:

[0019] Get the weight of the largest ton bag ;

[0020] Obtain the weight of the lifting device for the electric hoist ;

[0021] Obtain the design rated lifting capacity Q= + When selecting a wire rope electric hoist as the electric lifting machine, its rated lifting capacity must be higher than Q.

[0022] Determining the lifting speed and motor power of the electric hoist includes:

[0023] The height H of the powder silo in the concrete mixing plant was measured on-site. The height of the powder silo is the distance from the ground to the working platform on the top of the powder silo.

[0024] Set the lifting time T1 in the target single cycle time T, where the lifting time T1 is controlled within 1 minute. The target single cycle time T includes the hooking time, lifting time, unloading time, descent time and unhooking time of the electric hoist; thereby obtaining the required lifting speed v≥H / T1;

[0025] Therefore, the standard is for wire rope electric hoists with a lifting speed not lower than the required lifting speed v;

[0026] The static power of the motor of the electric hoist is checked using the following formula:

[0027] ;

[0028] Where P is the static power of the electric hoist motor; Q is the rated lifting capacity of the electric hoist; g is the acceleration due to gravity; v is the lifting speed of the electric hoist; 1000 is the unit conversion factor; η is the total transmission efficiency of the wire rope electric hoist; and 60 is the time conversion factor.

[0029] Therefore, the motor power of the electric hoist must be higher than the static power of the electric hoist motor.

[0030] The safety check of the wire rope of the wire rope electric hoist includes:

[0031] The working class of the wire rope of the electric wire rope hoist is set to M4, and its safety factor n≥6 is required.

[0032] Calculate the minimum breaking tensile force of the wire rope ≥Q·g·n;

[0033] Select the wire rope that meets the minimum breaking strength requirement. The required steel wire rope.

[0034] Preferably, the method for determining the opening size includes:

[0035] Determine the opening size as a square hole of 800 mm × 800 mm;

[0036] The opening location should be selected on the top plane of the powder silo in the concrete mixing plant, close to the edge but far away from the dust collector, safety valve and level gauge on the top of the silo, and ≥500 mm away from the silo wall.

[0037] Preferably, the opening is reinforced, and the method of opening reinforcement specifically includes:

[0038] The equal-area reinforcement method is used to reinforce the opening with reinforcing rings. The reinforcing rings are placed around the opening at the top of the silo, completely covering the edge of the opening, and the center of the reinforcing rings coincides with the center of the opening.

[0039] Preferably, the main beam of the grille is made of 12# channel steel, the secondary beam is made of 50×5 angle steel, and the mesh spacing is about 150mm.

[0040] Preferably, the bag breaker is made of high-strength wear-resistant steel plate NM400. The bag breaker with a four-sided pyramidal structure is welded from four triangular NM400 steel plates. The apex angle of the four-sided pyramidal structure is about 60°. The overall height of the bag breaker is 400mm. The bottom of the bag breaker is bolted to the grid or special base through a flange. Longitudinal reinforcing ribs are added to the inner side of the four triangular NM400 steel plates.

[0041] Preferably, the dustproof sealing system is a double sealing system, which includes a soft curtain sealing sleeve. Above the opening, a square soft curtain sleeve made of wear-resistant rubber cloth is fixed, with its lower end fixed to the edge of the opening and its upper end being a free end. The double sealing system also includes a negative pressure dust suction port: a short dust suction pipe is added to the top of the silo near the opening and is connected to the air inlet of the existing pulse bag dust collector on the top of the silo through the pipe.

[0042] Preferably, the electrical control system includes:

[0043] The main power supply circuit includes three-phase AC power supplies L1, L2, L3, and circuit breaker QF;

[0044] The power actuation components include the lifting motor M of the electric hoist and the lowering motor M of the electric hoist;

[0045] The control circuit components include a control transformer TC and control buttons, including an up button SB1, a down button SB2 and an emergency stop button SB0.

[0046] Safety protection components include an upper limit switch SQ1, a lower limit switch SQ2, a thermal relay FR, and an overload limiter SL;

[0047] Auxiliary components include time relay KT, buzzer HA, rising contactor KM1, and falling contactor KM2;

[0048] Three-phase power supplies L1, L2, and L3 are connected sequentially to the incoming terminals of circuit breaker QF;

[0049] The output terminals of the circuit breaker QF are respectively connected to the main contact input terminals of the rising contactor KM1 and the falling contactor KM2;

[0050] The main contact output terminals of KM1 and KM2 are connected in parallel and then connected to the input terminal of thermal relay FR;

[0051] The output terminal of the thermal relay FR is directly connected to the drive motor M of the electric hoist;

[0052] The motor casing is reliably grounded to PE to achieve leakage protection;

[0053] The primary side of the control transformer TC is connected to any two phases of a three-phase power supply, and the secondary side outputs a 36V safety control voltage.

[0054] The positive terminal of the secondary side of transformer TC is first connected to the normally closed contact of emergency stop button SB0;

[0055] The normally closed contact of the thermal relay FR is connected in series in the main incoming line of the control circuit, and disconnects the entire control circuit when the motor is overloaded.

[0056] The normally closed contact of the overload limiter SL is connected in series in the common circuit of KM1 and KM2 coils, and cuts off the lifting action when overloaded.

[0057] The coil of the time relay KT is connected in parallel with the coil of the rising contactor KM1. When KM1 is energized, KT will start timing synchronously.

[0058] The normally closed auxiliary contact of KM1 is connected in series with the coil circuit of KM2, and the normally closed auxiliary contact of KM2 is connected in series with the coil circuit of KM1 to prevent short circuits caused by simultaneous lifting and lowering.

[0059] Preferably, the process flow of the ton bag powder feeding control system for concrete mixing plants includes:

[0060] An electric hoist lifts ton bags of cement to the top of the powder silo in the concrete mixing plant.

[0061] The bottom of the cement-filled ton bag contacts a bag breaker fixed to the powder silo of the concrete mixing plant to cut it open.

[0062] Cement falls directly into the powder silo of the concrete mixing plant by gravity;

[0063] The empty ton bags are lowered and recycled.

[0064] The beneficial effects of the present invention are as follows, compared with the prior art:

[0065] This invention proposes a vertical lifting method to replace horizontal pneumatic conveying, and a gravity unloading method to replace mechanical airlock feeding. By hoisting the entire ton bag to the top of the silo and unloading it directly by gravity, the high-speed wear and tear and the need for airlocking in the powder conveying process are completely eliminated, achieving a significant simplification of the process and a qualitative leap in reliability. The system's continuous feeding capacity is greatly improved compared to existing technologies, completely solving the supply bottleneck. Dust concentration in the working area is reduced, eliminating dust pollution caused by leakage from the rotary unloading valve at the source, significantly improving the working environment. The expected lifespan of the bag breaker is longer than that of existing rotary unloading valves. The economic benefits are extremely outstanding. Attached Figure Description

[0066] Figure 1 This is a system process flow diagram of the existing technology;

[0067] Figure 2 This is a process flow diagram of the concrete mixing plant ton bag powder feeding control system of the present invention.

[0068] Figure 3 This is a front view of the concrete mixing plant ton bag powder feeding control system of the present invention.

[0069] Figure 4 This is a side view of the concrete mixing plant ton bag powder feeding control system of the present invention;

[0070] Figure 5 This is a partial circuit diagram of the electrical control system of the present invention. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0072] like Figures 1 to 5 As shown, this invention proposes a feeding control system for ton bag powder materials in a concrete mixing plant, comprising the following steps:

[0073] The FQS-20 ton bag unpacking system, commonly used in existing concrete mixing plants, combines ton bag unpacking with pneumatic conveying. The system mainly consists of an unpacking platform, a mechanical bag-breaking device, a buffer hopper, a rotary discharge valve, a Roots blower, and conveying pipelines. The unpacking platform is used by forklifts to place the ton bags, while the mechanical bag-breaking device below has built-in blades that can cut open the bottom of the ton bags. After the bags are broken, the cement falls into the buffer hopper and is then quantitatively fed through a rotary discharge valve (6L / rev, 2.2kW) using a pneumatic conveying system. The high-pressure airflow generated by the Roots blower (SSR-150 type, air volume 28.5m³ / min, air pressure 49kPa, power 45kW) conveys the material through a DN150 seamless steel pipe (approximately 25 meters in total length, including multiple 90° bends) to the top of the silo for storage.

[0074] The process can be summarized as follows: forklift loading bags → ton bag positioning and sealing → bag breaking → cement falling into the buffer hopper → rotary unloading valve feeding → Roots blower airflow conveying → through pipeline to the top of the silo for storage.

[0075] To objectively evaluate performance, a 72-hour continuous production tracking test of the existing technology system was conducted (starting from August 15, 2024), and the data is summarized in Table 1.

[0076] Table 1. Segmented Test Record of Feeding Efficiency of the Original Packaging Unpacking Machine System

[0077]

[0078] The following conclusions can be drawn from the above test data: First, the actual capacity of the system is severely insufficient, with an overall average efficiency of only 4.44 t / h, which is less than a quarter of the design capacity (20 t / h); second, the efficiency decay trend is extremely obvious, continuously decreasing from 5.25 t / h in the initial stage to 4.0 t / h in the final stage, indicating that the system performance is extremely unstable; more importantly, the analysis revealed that the main time consumption is concentrated in the material conveying stage, and attempts to improve efficiency by increasing the fan pressure will only exacerbate component wear. This fully demonstrates that the pneumatic conveying stage and its airlock components are the fundamental bottleneck of the entire system.

[0079] The most prominent problem with this system is the extremely short lifespan of the rotary discharge valve. A new valve, after approximately 18-22 days of use, will exhibit uneven material discharge, airlock failure, and increased abnormal noise, necessitating replacement. Disassembly of the scrapped rotary discharge valves revealed typical failure characteristics: the clearance between the rotor blade tip and the inner wall of the housing had increased from approximately 0.1-0.2 mm at the factory to over 2 mm, with some areas on the blade side reaching 8 mm, resulting in a near-complete loss of airlock function; obvious grooved wear had formed on the inner wall of the housing in the direction of cement flow impact, damaging the original circular cavity; simultaneously, the valve shaft support bearing became stuck due to dust intrusion, causing shaft end seal failure and further exacerbating leakage.

[0080] Failure Mechanism Analysis: Based on the fundamental principles of pneumatic conveying, the rotary discharge valve performs two main functions in the system: uniform and quantitative feeding, and airlocking to prevent high-pressure airflow backflow. When the gap between the rotor blade tip and the housing increases due to wear, the airlocking function fails. The high-pressure airflow (49 kPa) generated by the Roots blower will backflow through the increased gap into the buffer hopper, disrupting the normal descent of material in the hopper, leading to poor discharge and reduced efficiency. It also blows out a large amount of dust from the hopper-to-bag interface, causing severe dust pollution. Simultaneously, internal leakage causes a short circuit in the conveying airflow, reducing the effective conveying volume and decreasing material conveying capacity. Cement particles (Mohs hardness approximately 3-4) are continuously impacted by the high-speed airflow (estimated at 25-30 m / s) with tremendous kinetic energy. The rate of this erosion wear is proportional to the 2nd to 3rd power of the particle impact velocity. Therefore, high-speed gas-solid two-phase flow erosion is the root cause of the short lifespan of the rotary discharge valve, and its failure directly leads to two major problems: reduced efficiency and excessive dust.

[0081] Addressing the three major challenges of complex processes, wear caused by high-speed conveying, and dust generation due to airlock failure, this paper proposes a structural principle of simplification, static control, and potential energy as the primary energy source. The underlying technology is to completely eliminate pneumatic conveying and utilize gravity for material transfer.

[0082] The system process of this invention adopts a simplified route of vertical lifting → bag breaking at the bottom → gravity entry into the silo. That is: an electric hoist lifts the ton bag to the top of the silo → the bottom of the bag contacts the fixed bag breaker and breaks it → cement falls directly into the silo by gravity → empty bags descend and are recovered.

[0083] Table 2 shows a comparison between the technical solutions of the present invention and the technical solutions of the prior art.

[0084] Table 2 Comparison between the technical solutions of the present invention and the prior art

[0085]

[0086] The structure of the concrete mixing plant ton bag powder feeding control system of the present invention is as follows:

[0087] Electric hoist 1 is installed on the outside of the side wall of the powder silo 2 in the concrete mixing plant;

[0088] In a preferred but non-limiting embodiment of the present invention, the I-beam running track of the electric hoist 1 is fixed to the bracket pre-welded to the side wall of the powder silo 2 of the concrete mixing plant by high-strength bolts to ensure horizontality and stability.

[0089] The electric hoist 1 is located on the side of the top working platform of the powder silo 2 in the concrete mixing plant, vertically covering the ground material loading area to the top bag breaking and unloading area of ​​the silo. It can vertically lift the ton bags from the ground to the top bag breaker of the powder silo in the concrete mixing plant to complete the unloading.

[0090] The H-beam running track is aligned with the center of the 800mm×800mm unloading opening at the top of the powder silo 2 of the concrete mixing plant, ensuring that the ton bags fall accurately to the bag breaking device.

[0091] In a preferred but non-limiting embodiment of the present invention, the selection and design of the electric hoist includes:

[0092] Determine the design rated lifting capacity, which includes:

[0093] Get the weight of the largest ton bag =1.5t (15kN);

[0094] Obtain the weight of the lifting equipment (special lifting frame, bag gripping mechanism) for the electric hoist. =0.3t (3kN);

[0095] Obtain the design rated lifting capacity Q= + =1.8t. Considering the dynamic load factor and safety margin, a wire rope electric hoist is selected as the electric hoist. Its rated lifting capacity must be higher than Q, just as a wire rope electric hoist with Q=2.0t is selected.

[0096] Determining the lifting speed and motor power of the electric hoist includes:

[0097] The actual measured height of the powder silo 2 of the concrete mixing plant is H=15m. The height of the powder silo 2 of the concrete mixing plant is the distance from the ground to the working platform on the top of the powder silo 2 of the concrete mixing plant.

[0098] Set the lifting time T1 within the target single-cycle time T < 3 min (180 s), where the lifting time T1 is controlled within 1 minute. The target single-cycle time T includes the hooking time, lifting time, unloading time, descent time, and unhooking time of the electric hoist; thereby obtaining the required lifting speed v ≥ H / T1, for example...

[0099] v≥15m / 60s=0.25m / s=15m / min;

[0100] Therefore, the standard lifting speed of the wire rope electric hoist is not lower than the required lifting speed v. For example, the standard lifting speed of the CD1 type 2t-18m wire rope electric hoist is 8m / min.

[0101] The static power of the electric hoist motor is checked (according to GB / T3811 standard), and the check formula is as follows:

[0102] ;

[0103] Where P is the static power of the electric hoist motor; Q is the rated lifting capacity of the electric hoist; g is the gravitational acceleration, which is 9.81 m / s²; v is the lifting speed of the electric hoist; 1000 is the unit conversion factor to convert W to kW; η is the total transmission efficiency of the wire rope electric hoist; and 60 is the time conversion factor to convert minutes to seconds.

[0104] Therefore, the motor power of the electric hoist must be higher than the static power of the electric hoist motor, for example... After calculation, P≈3.08kW, so a standard motor with a rated power of 4.0kW is selected, and the safety factor meets the requirements;

[0105] The safety check of the wire rope of the wire rope electric hoist includes:

[0106] The working class of the wire rope of the electric wire rope hoist is set to M4, and its safety factor n≥6 is required.

[0107] Calculate the minimum breaking tensile force of the wire rope ≥Q·g·n, for example ≥Q·g·n=2000×9.81×6=117.72 kN;

[0108] Select the wire rope that meets the minimum breaking strength requirement. The required wire rope. For example, if the selected wire rope is 6×37+FC-13-1770-I-ZS, its nominal tensile strength is 1770 MPa, its diameter is 13 mm, and its minimum breaking strength is 118 kN > 117.72 kN, which meets the requirements.

[0109] An opening is provided at the top of the powder silo 2 of the concrete mixing plant;

[0110] In a preferred but non-limiting embodiment of the present invention, the method for determining the opening size includes:

[0111] Based on the standard ton bag being punctured and the resulting unloading port having a diameter of approximately Φ600 mm, to ensure sufficient swaying space during unloading and to avoid scratching, the opening size was determined to be a square hole of 800 mm × 800 mm.

[0112] The opening location should be selected on the top plane of the powder silo of the concrete mixing plant, close to the edge but far away from the dust collector, safety valve and level gauge on the silo top, and ≥500 mm away from the silo wall, so as to facilitate operation and not affect other equipment on the silo top.

[0113] In a preferred but non-limiting embodiment of the present invention, the opening is reinforced, and the method for reinforcing the opening specifically includes:

[0114] The opening weakens the structure and requires reinforcement. An equal-area reinforcement method (referring to the equal-area method principle for pressure vessel opening reinforcement) is used, applying reinforcing rings around the opening at the top of the silo, completely covering the edge of the opening. The center of the reinforcing ring coincides with the center of the opening to ensure uniform reinforcement.

[0115] For example, given the following conditions: silo diameter D = 3200 mm, silo top plate thickness δ = 8 mm, material Q235B (allowable stress at room temperature [σ] = 113 MPa), and the required reinforcement area for the opening.

[0116] A = d × δ = 800 × 8 = 6400 mm², where d is the diameter of the opening;

[0117] Therefore, the outer diameter of the reinforcing ring is 1.5 times the opening diameter, i.e., 1200mm, and the inner diameter of the reinforcing ring is the same as the opening diameter (800mm). For simplicity and effectiveness, the reinforcing ring is made of Q235B steel plate of the same material as the silo top plate, and the thickness of the reinforcing ring is... =12mm (greater than the thickness of the top plate);

[0118] Metal area provided by the reinforcing ring =(1200-800)×12=4800mm². Furthermore, the top plate of the silo surrounding the opening also has a certain reinforcing capacity. It is generally considered that the effective reinforcement width is twice the diameter of the opening. After calculation, the total effective reinforcement area is greater than the required reinforcement area, and the strength meets the requirements.

[0119] The reinforcing ring and the top plate of the silo are welded together with double-sided continuous fillet welds, with a weld leg height of 8mm, to ensure strength and sealing.

[0120] A grid made of welded steel is installed above the opening to support the ton bags and guide them to fall onto the bag breaker, while also facilitating personnel to stand and work.

[0121] In a preferred but non-limiting embodiment of the present invention, the main beam of the grille is made of 12# channel steel, the secondary beam is made of 50×5 angle steel, and the mesh spacing is approximately 150mm.

[0122] Bag-breaking device 3 with a four-sided pyramid structure;

[0123] In the preferred but non-limiting embodiment of this invention, the bag breaker is the only component in this solution that directly contacts the material and is subject to wear. Its design and material selection are crucial. Based on the wear-resistant component design principles of the mechanical design manual, to address the potential presence of hard mineral particles in cement, high-strength wear-resistant steel plate NM400 is selected. Its Brinell hardness (HBW) reaches approximately 400, and its tensile strength is ≥1200MPa, exhibiting good wear resistance and a certain degree of impact resistance. The bag breaker, with its pyramidal structure, is welded from four triangular NM400 steel plates (20mm thick). The apex angle of the pyramid is approximately 60°. This angle ensures successful piercing of ton bags (usually polypropylene woven bags) while providing sufficient strength and support thickness for the blade edge, preventing it from becoming too thin and prone to chipping. The overall height of the bag breaker is approximately 400mm. The bottom of the bag breaker is bolted to a grating or a dedicated base via a flange for easy replacement after wear. Longitudinal reinforcing ribs are added to the inner side of the four triangular NM400 steel plates to improve overall rigidity and prevent deformation under impact.

[0124] A dustproof sealing system installed next to the opening;

[0125] In a preferred but non-limiting embodiment of the present invention, the dustproof sealing system is a double sealing system. Although gravity unloading is used, a double sealing system is designed to ensure a clean working environment and prevent dust from escaping from the top of the silo during unloading. The double sealing system includes a soft curtain sealing sleeve, above an 800mm×800mm opening, a square soft curtain sleeve made of wear-resistant rubber cloth is fixed, with its lower end fixed to the edge of the opening and its upper end free. When the ton bag is lifted into the square soft curtain sleeve, the soft curtain naturally wraps around the outside of the ton bag, forming a dynamic sealing channel. The double sealing system also includes a negative pressure dust suction port: a Φ150mm short suction pipe is added to the top of the silo near the opening, connected to the air inlet of the existing pulse bag dust collector on the top of the silo. During unloading, the dust collector is activated, forming a slight negative pressure (-50Pa~-100Pa) in the unloading port area, sucking in any small amount of dust that may escape for treatment. Third, the expected effect: By combining physical soft sealing and airflow negative pressure sealing, the unloading dust can be effectively controlled within the closed system, and it is expected to reduce the dust concentration at the operating position by more than 85%.

[0126] The electrical control system that connects to the motor of the wire rope electric hoist.

[0127] In a preferred but non-limiting embodiment of the present invention, the electrical control system prioritizes simplicity, reliability, and safety, and mainly consists of a power section, a control section, a protection and detection section, and an auxiliary section. The power section includes the main circuit of the electric hoist (including a circuit breaker, contactor, and thermal relay); the control section comprises a control box with an IP55 protection rating, up / down buttons, and an emergency stop button; the protection and detection section is equipped with upper and lower limit switches (LXK3-20S type) and an overload limiter (0-3t range, with 4-20mA output and audible and visual alarm functions); the auxiliary section includes a unloading time relay (used to control the unloading holding time) and lighting. The system's control logic is designed for a simple and reliable operation: after the operator connects the lifting device to the ton bag, they press the "up" button, and the electric hoist immediately lifts the ton bag, automatically stopping when it reaches the preset upper limit at the top of the silo. At this point, the ton bag rests on the bag breaker and begins unloading, while the time relay starts timing (set to 60-90 seconds, adjustable as needed). After the timer expires, a buzzer sounds, and the operator presses the "Lower" button. The empty bag descends to the ground and automatically stops at the lower limit. During operation, if overload occurs, the overload limiter will immediately cut off the lifting circuit and issue an alarm. In terms of safety features, the system has multiple protection functions including short circuit, overload, phase loss, and limit switches to ensure safe and reliable operation. Furthermore, the control voltage uses a safe voltage (e.g., 36V), further enhancing operator safety. Specifically, this includes:

[0128] The main power supply circuit includes a three-phase AC power supply (L1, L2, L3) and a circuit breaker QF;

[0129] The power actuation components include the lifting motor M of the electric hoist and the lowering motor M of the electric hoist (the same motor rotates in both directions).

[0130] The control circuit components include a control transformer TC and control buttons, including an up button SB1, a down button SB2 and an emergency stop button SB0.

[0131] Safety protection components include an upper limit switch SQ1, a lower limit switch SQ2, a thermal relay FR, and an overload limiter SL;

[0132] Auxiliary components include time relay KT, buzzer HA, rising contactor KM1, and falling contactor KM2;

[0133] The overall connection structure of the electrical control system is as follows: main power supply → circuit breaker → contactor main contacts → thermal relay → electric hoist motor;

[0134] Control power supply → Control transformer → Emergency stop button → Limit switch → Control button → Contactor coil → Protective element → Neutral wire.

[0135] Three-phase power supplies L1, L2, and L3 are connected sequentially to the incoming terminals of circuit breaker QF;

[0136] The output terminals of the circuit breaker QF are respectively connected to the main contact input terminals of the rising contactor KM1 and the falling contactor KM2;

[0137] The main contact output terminals of KM1 and KM2 are connected in parallel and then connected to the input terminal of thermal relay FR;

[0138] The output terminal of the thermal relay FR is directly connected to the drive motor M of the electric hoist;

[0139] The motor casing is reliably grounded to PE to achieve leakage protection;

[0140] The primary side of the control transformer TC is connected to any two phases of a three-phase power supply, and the secondary side outputs a 36V safety control voltage.

[0141] The positive terminal of the secondary side of transformer TC is first connected to the normally closed contact of emergency stop button SB0;

[0142] The emergency stop button SB0 output terminal is divided into two paths:

[0143] One path → normally closed contact of upper limit switch SQ1 → normally open contact of up button SB1 → coil of up contactor KM1 → neutral wire;

[0144] One path → normally closed contact of lower limit switch SQ2 → normally open contact of down button SB2 → coil of down contactor KM2 → neutral wire;

[0145] The normally closed contact of the thermal relay FR is connected in series in the main incoming line of the control circuit, and disconnects the entire control circuit when the motor is overloaded.

[0146] The normally closed contact of the overload limiter SL is connected in series in the common circuit of KM1 and KM2 coils, and cuts off the lifting action when overloaded.

[0147] The coil of the time relay KT is connected in parallel with the coil of the rising contactor KM1. When KM1 is energized, KT will start timing synchronously.

[0148] Time relay KT delays and closes normally open contact → buzzer HA → neutral line, buzzer alarm sounds after unloading timer expires;

[0149] All control component housings and control box housings are grounded to PE.

[0150] The normally closed auxiliary contact of KM1 is connected in series with the coil circuit of KM2, and the normally closed auxiliary contact of KM2 is connected in series with the coil circuit of KM1 to prevent short circuits caused by simultaneous lifting and lowering.

[0151] SQ1 and SQ2 are normally closed, and the corresponding contactor coils will automatically disconnect when the limit position is reached.

[0152] When the overload limiter SL detects a load of ≥3t, the contact opens, forcibly cutting off the lifting control.

[0153] The thermal relay FR detects motor overload and disconnects the main control circuit for shutdown protection.

[0154] Emergency stop SB0 is normally closed. Pressing it will immediately cut off the entire control circuit, and all actions will stop immediately.

[0155] Pressing the lift button SB1 → KM1 coil is energized → main contacts close → motor rotates forward and lifts; simultaneously, KT timing occurs.

[0156] When the upper limit SQ1 is reached, SQ1 disconnects, KM1 loses power, lifting stops, and unloading begins.

[0157] KT timer expires → contact closes → HA buzzer sounds;

[0158] Press down SB2 → KM2 coil is energized → main contacts close → motor reverses and descends;

[0159] When the lower limit SQ2 is reached, SQ2 disconnects, KM2 loses power, and the descent stops.

[0160] Overload / Excessive load / Emergency stop → Corresponding protection contact opens → System shuts down immediately.

[0161] In a preferred but non-limiting embodiment of the present invention, the process flow of the ton bag powder feeding control system for a concrete mixing plant includes:

[0162] An electric hoist lifts ton bags of cement to the top of the powder silo in the concrete mixing plant.

[0163] The bottom of the cement-filled ton bag contacts a bag breaker fixed to the powder silo of the concrete mixing plant to cut it open.

[0164] Cement falls directly into the powder silo of the concrete mixing plant by gravity;

[0165] The empty ton bags are lowered and recycled.

[0166] A specific embodiment of the present invention is shown below:

[0167] The construction of the ton bag powder feeding control system for the concrete mixing plant was carried out intensively from October 20th to 26th, 2024, lasting 7 days, and was staggered with the production schedule to minimize the impact on production. The first two days focused on building and securing the work platform on top of the silo, including precisely marking and cutting 800mm x 800mm square holes in the silo roof according to the design drawings, followed by installing and welding reinforcing rings. The third day focused on installing the electric hoist: first, the I-beam running track was fixed to the brackets pre-welded to the silo sidewall with high-strength bolts, ensuring its levelness and stability, and then the electric hoist body was hoisted and secured. The fourth day involved fabricating and installing the silo roof grating platform and bag breaker base, hoisting the welded NM400 bag breaker into place and tightening it with bolts. The fifth day involved laying electrical wiring, installing the control box, limit switches, overload sensors, and other electrical components, and completing the wiring. On the sixth day, dustproof soft curtain sealing sleeves were fabricated and installed, and negative pressure dust collection pipes were connected to the dust collector on the top of the silo. On the final day, the system underwent no-load and load testing, including no-load up / down and limit tests of the electric hoist, a static load test at 125% rated load (2.5 tons) (strictly adhering to GB / T5905 "Crane Test Specifications and Procedures"), and a full-process test of actual bag breaking and unloading using ton bags filled with sand. Time relay parameters were adjusted, and the sealing effect was checked. The entire construction process strictly adhered to safety regulations for high-altitude operations and hot work, and no safety accidents occurred.

[0168] After the system was officially put into operation, a special efficiency test was organized on November 5, 2024. Thirty fully loaded ton bags (each weighing between 1.48 and 1.52 tons) were randomly selected, and a skilled operator continuously operated the system according to standard procedures, recording the time for each cycle. Some test data are shown in Table 3.

[0169] Table 3. Testing of the improved system's material feeding efficiency.

[0170]

[0171] Note: The "lifting time" and "lowering time" in the table include auxiliary time such as manual hooking and unhooking. The pure mechanical operation time (lifting + lowering) is approximately 220 seconds. The unloading time refers to the time from when the bag is broken to when the cement is basically empty, and is a key variable.

[0172] Therefore, the average cycle time is approximately 285 seconds (4.75 minutes), of which the effective unloading time is approximately 65 seconds, and the average efficiency is approximately 1.5 tons / (285 / 3600) hours ≈ 19.0 t / h.

[0173] The efficiency measured in this test is the single-bag cycle efficiency. In reality, the system's greatest advantage lies in its ability to operate in parallel and with virtually uninterrupted continuous operation. When two operators work together, one hooks the bag on the ground while the other monitors unloading and directs the descent from the top of the silo, a continuous production line operation can be achieved with one bag unloading while another is being raised / lowered. In this mode, the system's sustainable feeding capacity is determined by the slowest stage (unloading time). Theoretically, it can process approximately 3600 bags per hour / 65 seconds ≈ 55 bags. Therefore, the system's maximum sustainable feeding capacity can reach 55 bags / hour × 1.5 tons / bag ≈ 82.5 t / h. Considering factors such as actual coordination and bag type differences, a conservative estimate suggests that its sustainable and stable feeding capacity is no less than 50 t / h, more than 10 times that of the original system (5 t / h), fully meeting or even far exceeding production needs.

[0174] In summary, the improved system not only maintains stable single-cycle efficiency, but also achieves an order-of-magnitude increase in sustainable material feeding capacity due to its unique parallel operation mode, fundamentally solving the supply bottleneck of the original system.

[0175] To objectively assess the environmental benefits after the system's construction, the project team conducted comparative testing of the work environment using a calibrated portable dust detector, following the testing methods outlined in the "Occupational Exposure Limits for Hazardous Factors in the Workplace" (GBZ2.1-2019) after the system had stabilized. Although no formal report was commissioned from a third-party organization, the results of the comparative testing at the same locations using the same instruments effectively reflect the system's dust control performance. Sampling points were set at the operator's breathing zone height, the top surface of the silo, and 5 meters downwind. The test results are shown in Table 4.

[0176] Table 4. Comparison of dust concentration in the working environment before and after construction (mg / m³)

[0177]

[0178] Table 4 shows that the improved system reduced the average dust concentration at each monitoring point by more than 85%, fundamentally improving the working environment. Although the values ​​at individual points are still slightly higher than the national standard, they are very close. Analysis suggests this is mainly due to tiny gaps between the flexible curtain sealing sleeve and the outer wall of the ton bag. In the future, by optimizing the material and structure of the flexible curtain (such as using memory foam sealing strips) or slightly increasing the dust collector's airflow, it is expected that the standard can be fully met.

[0179] The wear condition of the bag breaker, the core wear-resistant component of the new system, is a crucial indicator of design success. A regular monitoring plan was established, with the remaining thickness of the four blade tips measured every 15 days using calipers. As of December 30, 2024 (60 days after commissioning), the monitoring data trends are shown in Table 5.

[0180] Table 5. Monitoring Record of Wear on the Blade Edge of the Bag Breaker

[0181]

[0182] The monitoring data shows that the wear rate is very low and stable, averaging about 0.043 mm per day. Based on this rate, it would take approximately 233 days for the initial 20 mm wear to reach the critical thickness affecting bag breaking (assuming 10 mm). Considering the possibility of changes in the wear rate later in the process, a conservative estimate suggests that the bag breaker's lifespan could reach over 400 days (approximately 13 months), which is 20 times longer than the original system's rotary discharge valve (20 days).

[0183] As of January 30, 2025, the system has been running continuously without failure for more than 90 days.

[0184] Total material delivered: approximately 12,000 tons of cement.

[0185] Unplanned downtime: 0 times. No concrete production interruptions occurred due to malfunctions in the feeding system.

[0186] Routine maintenance: Only routine wire rope lubrication checks and limit switch function tests were performed; no major components were replaced.

[0187] Operational feedback: Operators said the new system is simple and easy to understand, the workload has not increased (no need to frequently clean pipes and replace valves), and the working environment has been greatly improved.

[0188] All materials for this renovation were procured independently, and the construction was mainly carried out by our own skilled workers. The total investment details are clearly shown in Table 6.

[0189] Table 6. Detailed List of System Upgrade Investments

[0190]

[0191] After the renovation, the composition of operating costs underwent a fundamental change, as detailed in Table 7.

[0192] Table 7 Comparative Analysis of Annual Operating Costs (Unit: Yuan)

[0193]

[0194] As shown above, the system energy consumption has been improved: the electric hoist is 4kW, with an average daily actual operating time of about 4 hours (estimated based on a loading capacity of 100 tons and a cycle time of about 5 minutes per bag), operating for 250 days a year, and an electricity cost of 0.8 yuan / kWh: 4kW × 4h / day × 250 days × 0.8 yuan / kWh = 3,200 yuan. Table 7 shows that, based on on-site measurements, the electric hoist has an average daily effective operating time of about 3 hours, and the annual electricity cost is estimated to be about 2,400 yuan (a conservative estimate). Cost allocation for the bag breaker: the cost of a single bag breaker is about 2,000 yuan, with a lifespan of 400 days. The annual cost allocation is approximately (2,000 yuan / 400 days) × 250 days ≈ 1,250 yuan, rounded down to 1,000 yuan.

[0195] In addition, this specific embodiment also has the following indicators:

[0196] (1) Static payback period:

[0197] T = Total Investment / Annual Savings = 32400 / 295000 ≈ 0.11 years

[0198] The above values ​​are based on static theoretical calculations. Considering actual construction, commissioning, and production coordination, the actual investment payback period for the project is approximately 3.1 months.

[0199] (2) Net Present Value (NPV) Analysis (considering a 5-year period, discount rate of 8%):

[0200] Initial investment: -32,400 yuan.

[0201] Annual net cash flow (savings): 295,000 yuan.

[0202] 5-year net present value: NPV = -32,400 + 295,000 × (P / A, 8%, 5) ≈ -32,400 + 295,000 × 3.9927 ≈ 1,145,000 yuan.

[0203] (3) Internal rate of return (IRR): It is much higher than the benchmark rate of return of general industrial projects, and its economic benefits are extremely significant.

[0204] This specific implementation is a typical example of a technological upgrade with "significant economic benefits." With an initial investment of only about 32,400 yuan, the cost was recovered in a very short time, and it saves the mixing plant nearly 300,000 yuan in operating expenses annually, demonstrating excellent economic benefits.

[0205] This invention innovatively simplifies the traditional multi-stage, complex process of unpacking, buffering, conveying, and warehousing into a two-stage process of lifting and unpacking combined with gravity-driven direct warehousing, significantly reducing potential failure points at the system level. It abandons the high-energy-consuming mode of converting large amounts of electrical energy into gas kinetic energy for material conveying, cleverly utilizing a small amount of electrical energy to lift the material, increasing its potential energy, and then relying on gravity potential energy to naturally complete unloading, aligning with the green concept of energy conservation and emission reduction. The focus of wear-resistant design shifts from resisting high-speed impacts to avoiding them altogether. By altering the material flow pattern, critical contact components only experience low-speed sliding friction, allowing for ultra-long service life with conventional wear-resistant materials (NM400) at a controllable cost.

[0206] In summary, the design philosophy of simplifying complexity and returning to the physical essence practiced in this invention solves the technical problems in specific scenarios. In view of the weak maintenance capabilities in remote overseas areas, it proposes a simplified design paradigm with high reliability and low maintenance dependence.

[0207] The beneficial effects of the present invention are as follows, compared with the prior art:

[0208] This invention proposes a vertical lifting method to replace horizontal pneumatic conveying, and a gravity unloading method to replace mechanical airlock feeding. By hoisting the entire ton bag to the top of the silo and unloading it directly by gravity, the high-speed wear and tear and the need for airlocking in the powder conveying process are completely eliminated, achieving a significant simplification of the process and a qualitative leap in reliability. The system's continuous feeding capacity is greatly improved compared to existing technologies, completely solving the supply bottleneck. Dust concentration in the working area is reduced, eliminating dust pollution caused by leakage from the rotary unloading valve at the source, significantly improving the working environment. The expected lifespan of the bag breaker is longer than that of existing rotary unloading valves. The economic benefits are extremely outstanding.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention without departing from the spirit and scope of the present invention. Any modifications or equivalent substitutions should be covered within the scope of protection of the claims of the present invention.

Claims

1. A feeding control system for ton-bag powder materials in a concrete mixing plant, characterized in that, include: An electric hoist is installed on the outside of the side wall of the powder silo in a concrete mixing plant. An opening is provided at the top of the powder silo in the concrete mixing plant. A grid made of welded steel sections is installed above the opening to hold the ton bags and guide them to fall onto the bag breaker. A bag-breaking device with a four-sided pyramidal structure; A dustproof sealing system installed next to the opening; The electrical control system that connects to the motor of the wire rope electric hoist; The I-beam running track of the electric hoist is fixed to the bracket support pre-welded to the side wall of the powder silo of the concrete mixing plant by high-strength bolts; The electric hoist is located on the top working platform of the powder silo in the concrete mixing plant. It can vertically lift the ton bags from the ground to the top of the bag breaker in the powder silo of the concrete mixing plant for unloading. The H-beam running track is directly aligned with the center of the unloading opening at the top of the powder silo of the concrete mixing plant; The selection and design of electric hoists includes: Determine the design rated lifting capacity, which includes: Get the weight of the largest ton bag ; Obtain the weight of the lifting device for the electric hoist ; Obtain the design rated lifting capacity Q= + When selecting a wire rope electric hoist as the electric lifting machine, its rated lifting capacity must be higher than Q. Determining the lifting speed and motor power of the electric hoist includes: The height H of the powder silo of the concrete mixing plant was measured on site. The height of the powder silo of the concrete mixing plant is the distance from the ground to the working platform on the top of the powder silo.

2. Set the lifting time T1 in the target single cycle time T, where the lifting time T1 is controlled within 1 minute. The target single cycle time T includes the hooking time, lifting time, unloading time, descent time and unhooking time of the electric hoist; thereby obtaining the required lifting speed v≥H / T1; Therefore, the standard is for wire rope electric hoists with a lifting speed not lower than the required lifting speed v; The static power of the motor of the electric hoist is checked using the following formula: ； Where P is the static power of the electric hoist motor; Q is the rated lifting capacity of the electric hoist; g is the acceleration due to gravity; v is the lifting speed of the electric hoist; 1000 is the unit conversion factor; η is the total transmission efficiency of the wire rope electric hoist; and 60 is the time conversion factor. Therefore, the motor power of the electric hoist must be higher than the static power of the electric hoist motor. The safety check of the wire rope of the wire rope electric hoist includes: The working class of the wire rope of the electric wire rope hoist is set to M4, and its safety factor n≥6 is required. Calculate the minimum breaking tensile force of the wire rope ≥Q·g·n; Select the wire rope that meets the minimum breaking strength requirement. The required wire rope; Methods for determining the opening size include: Determine the opening size as a square hole of 800 mm × 800 mm; The opening location should be selected on the top plane of the powder silo in the concrete mixing plant, close to the edge but far away from the dust collector, safety valve and level gauge on the top of the silo, and ≥500 mm away from the silo wall.

3. Reinforce the opening. Specific methods for opening reinforcement include: The equal-area reinforcement method is used to reinforce the opening with reinforcing rings. The reinforcing rings are placed around the opening at the top of the silo, completely covering the edge of the opening, and the center of the reinforcing rings coincides with the center of the opening.

4. The concrete mixing plant ton bag powder feeding control system according to claim 1, characterized in that, The main beam of the grating is made of 12# channel steel, the secondary beam is made of 50×5 angle steel, and the mesh spacing is about 150mm.

5. The concrete mixing plant ton bag powder feeding control system according to claim 2, characterized in that, The bag breaker is made of high-strength wear-resistant steel plate NM400. The bag breaker with a four-sided pyramidal structure is welded from four triangular NM400 steel plates. The apex angle of the pyramidal structure is about 60°. The overall height of the bag breaker is 400mm. The bottom of the bag breaker is bolted to the grid or special base through a flange. Longitudinal reinforcing ribs are added to the inside of the four triangular NM400 steel plates.

6. The concrete mixing plant ton bag powder feeding control system according to claim 3, characterized in that, The dustproof sealing system is a double sealing system, which includes a soft curtain sealing sleeve. Above the opening, a square soft curtain sleeve made of wear-resistant rubber cloth is fixed, with its lower end fixed to the edge of the opening and its upper end being a free end. The double sealing system also includes a negative pressure dust suction port: a short dust suction pipe is added to the top of the silo near the opening, which is connected to the air inlet of the existing pulse bag dust collector on the top of the silo through a pipe.

7. The concrete mixing plant ton bag powder feeding control system according to claim 4, characterized in that, The electrical control system includes: The main power supply circuit includes three-phase AC power supplies L1, L2, L3, and circuit breaker QF; The power actuation components include the lifting motor M of the electric hoist and the lowering motor M of the electric hoist; The control circuit components include a control transformer TC and control buttons, including an up button SB1, a down button SB2 and an emergency stop button SB0. Safety protection components include an upper limit switch SQ1, a lower limit switch SQ2, a thermal relay FR, and an overload limiter SL; Auxiliary components include time relay KT, buzzer HA, rising contactor KM1, and falling contactor KM2; Three-phase power supplies L1, L2, and L3 are connected sequentially to the incoming terminals of circuit breaker QF; The output terminals of the circuit breaker QF are respectively connected to the main contact input terminals of the rising contactor KM1 and the falling contactor KM2; The main contact output terminals of KM1 and KM2 are connected in parallel and then connected to the input terminal of thermal relay FR; The output terminal of the thermal relay FR is directly connected to the drive motor M of the electric hoist; The motor casing is reliably grounded to PE to achieve leakage protection; The primary side of the control transformer TC is connected to any two phases of a three-phase power supply, and the secondary side outputs a 36V safety control voltage. The positive terminal of the secondary side of transformer TC is first connected to the normally closed contact of emergency stop button SB0; The normally closed contact of the thermal relay FR is connected in series in the main incoming line of the control circuit, and disconnects the entire control circuit when the motor is overloaded. The normally closed contact of the overload limiter SL is connected in series in the common circuit of KM1 and KM2 coils, and cuts off the lifting action when overloaded. The coil of the time relay KT is connected in parallel with the coil of the rising contactor KM1. When KM1 is energized, KT will start timing synchronously.

8. The normally closed auxiliary contact of KM1 is connected in series with the coil circuit of KM2, and the normally closed auxiliary contact of KM2 is connected in series with the coil circuit of KM1 to prevent short circuit when lifting and lowering are activated simultaneously.

9. The concrete mixing plant ton bag powder feeding control system according to claim 5, characterized in that, The process flow of the ton bag powder material feeding control system in a concrete mixing plant includes: An electric hoist lifts ton bags of cement to the top of the powder silo in the concrete mixing plant. The bottom of the cement-filled ton bag contacts a bag breaker fixed to the powder silo of the concrete mixing plant to cut it open. Cement falls directly into the powder silo of the concrete mixing plant by gravity; The empty ton bags are lowered and recycled.

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