Aggregate preheating device and method for concrete mixing station in severe cold high altitude area

Abstract

The invention discloses an aggregate preheating device and method for a concrete mixing station in a severe cold high altitude area, and relates to the technical field of hydropower station construction, the device comprises a preheating cylinder, a heating unit, a hot air circulation unit, a conveying unit and a control unit; the preheating cylinder is provided with a lower discharge port and an upper feed port; the heating unit comprises a gas heating assembly and an electric heating assembly; the hot air circulation unit comprises a heat circulation fan, a hot air pipeline and a hot air recovery assembly; one end of the hot air pipeline is connected with the inner side of the left end of the preheating barrel, and the other end of the hot air pipeline is connected with the gas heating assembly; an insulating layer is arranged on the inner wall of the preheating cylinder; the method comprises the steps of equipment initialization, aggregate conveying, heating mode selection, hot air circulation regulation and control, parameter dynamic adjustment, safety monitoring and discharging and shutdown. The device has the advantages that the device can be effectively applied to the unique severe-cold high-altitude environment, and the continuous production requirement of concrete is met.

Description

Technical Field

[0001] This invention relates to the field of hydropower station construction technology, and in particular to a preheating device and method for aggregates in concrete mixing plants in extremely cold and high-altitude areas. Background Technology

[0002] When constructing concrete in frigid, high-altitude regions, the low ambient temperature and air pressure cause the moisture in the concrete to freeze easily, resulting in slow strength gain or even failure to reach the design strength, severely impacting project quality. As a major component of concrete, the temperature of aggregates plays a crucial role in the concrete's discharge temperature and subsequent properties.

[0003] Currently, traditional concrete mixing plants mainly use two methods for preheating aggregates: direct heating and indirect heating.

[0004] Direct heating, such as directly baking aggregates with a flame, can lead to uneven heating, changes in aggregate composition, and environmental pollution. Indirect heating, if using conventional heat exchange devices, cannot be applied to the low-temperature environment of frigid, high-altitude regions. In such environments, conventional heat exchange devices have low heat exchange efficiency, making it difficult to quickly heat aggregates to a suitable temperature, and they also consume a lot of energy, which cannot actually meet the needs of continuous concrete production. Summary of the Invention

[0005] The purpose of this invention is to provide a preheating device and method for aggregates in concrete mixing plants located in frigid, high-altitude areas. This invention has the advantage of being effectively applied in the unique environment of frigid, high-altitude regions, meeting the needs of continuous concrete production.

[0006] The technical solution of the present invention: A preheating device for aggregates in a concrete mixing plant in frigid, high-altitude regions includes a preheating cylinder, a heating unit, a hot air circulation unit, a conveying unit, and a control unit. The preheating cylinder has a discharge port at its lower left end and a feed port at its upper right end. The heating unit includes a gas-fired heating element located at the right end of the preheating cylinder and electric heating elements distributed on the outer wall of the preheating cylinder. The hot air circulation unit includes a hot air circulation fan, a hot air duct, and a hot air recovery element located at the discharge port. One end of the hot air duct is connected to the inner side of the left end of the preheating cylinder, and the other end is connected to the gas-fired heating element. The hot air circulation fan is mounted on the hot air duct. The inner wall of the preheating cylinder is provided with an insulation layer.

[0007] In the aforementioned aggregate preheating device for concrete mixing plants in frigid, high-altitude areas, the conveying unit includes a drive motor located at the left end of the preheating cylinder and a spiral stirring shaft horizontally inserted into the preheating cylinder and connected to the output end of the drive motor.

[0008] In the aforementioned aggregate preheating device for concrete mixing plants in frigid, high-altitude regions, the gas heating component includes a gas burner and a gas inlet for introducing gas; the air outlet of the gas burner is connected to the preheating cylinder.

[0009] In the aforementioned aggregate preheating device for concrete mixing plants in frigid, high-altitude regions, the electric heating component is an electromagnetic heater or a resistance heater.

[0010] In the aforementioned aggregate preheating device for concrete mixing plants in frigid, high-altitude regions, the control unit includes a temperature sensor, a pressure sensor, a controller, and a display screen. The temperature sensors are respectively located inside the preheating cylinder, at the discharge port, and at the inlet port; The pressure sensor is located inside the preheating cylinder; The controller is electrically connected to the temperature sensor, pressure sensor, heating unit, hot air circulation unit, and conveying unit; The display screen is located on the control panel that is attached to the preheating cylinder.

[0011] In the aforementioned aggregate preheating device for concrete mixing plants in frigid, high-altitude areas, the insulation layer is a composite insulation structure, consisting of a ceramic fiber layer, an aluminum foil reflective layer, a rock wool layer, and a protective shell, arranged from the inside out. The composite insulation structure is fixed to the inner wall of the preheating cylinder by a high-temperature resistant adhesive, and the protective shell is connected to the flange of the preheating cylinder by bolts.

[0012] In the aforementioned aggregate preheating device for concrete mixing plants in frigid, high-altitude regions, the gas heating component further includes a gas leak detector, a flameout protection device, and an air ratio regulating valve; the gas leak detector is electrically connected to the control unit and transmits leak signals in real time; the flameout protection device is linked to the gas burner and automatically cuts off the gas supply when the burner is extinguished; the air ratio regulating valve is connected in series with the gas interface and its opening is adjusted by the control unit.

[0013] A method for preheating aggregates in a concrete mixing plant in frigid, high-altitude regions includes the following steps: S1. Equipment initialization: Start the controller, temperature and pressure sensors perform self-tests, the display shows the initial parameters, and an alarm signal is issued if the sensor is abnormal. S2. Aggregate conveying: The aggregate is fed into the preheating cylinder through the vibrating feeder at the inlet. The drive motor is started, which drives the spiral mixing shaft to rotate at a speed of 5-10 r / min. The aggregate moves to the left along the axial direction of the preheating cylinder. The gap between the spiral blades of the spiral mixing shaft and the inner wall of the preheating cylinder is maintained at 5-8 mm. S3, Heating Mode Selection: The controller selects the heating mode based on the initial aggregate temperature T0 detected by the temperature sensor at the feed inlet. When T0 < -20℃, activate the low-temperature mode: first start the gas burner, then introduce gas through the gas inlet, with an initial gas supply of 1.0-1.2m³. 3 / h, and at the same time start the electric heating component, with an initial power of 50-60kW; When -20℃≤T0<-10℃, the medium temperature mode is activated: the gas burner and electric heating components start synchronously, the gas supply is 0.7-1.0m³ / h, and the electric heating power is 40-50kW; When T0 ≥ -10℃, activate the normal temperature mode: only the electric heating element is activated, with a power of 30-40kW; S4. Hot air circulation control: When the hot air circulation fan is started, the hot air at the left end of the preheating cylinder is drawn back to the gas burner input end through the hot air pipe and mixed with the newly introduced gas for combustion; the hot air recovery component recovers the waste heat brought out by the aggregate at the discharge port and transfers the heat to the cold air pretreatment chamber at the feed port through the heat conduction pipe, preheating the cold air entering the cylinder to -5℃-0℃; S5. Dynamic parameter adjustment: The controller receives sensor signals in real time and dynamically adjusts the operating parameters. When the internal temperature T1 of the preheating cylinder is less than 3℃, increase the gas supply by 0.1-0.2m³. 3 / h or electric heating power 5-10kW; When T1 > 12℃, reduce the gas supply by 0.1-0.2m³. 3 / h or reduce the electric heating power by 5-10kW; When the internal air pressure P of the cylinder is less than 50 kPa, adjust the opening of the air ratio regulating valve to 80-90% to maintain the air-fuel ratio at 15:1 and ensure complete combustion of the fuel. When the discharge port temperature T2 deviates from the target value by ±1℃, adjust the spiral stirring shaft speed by ±1r / min and adjust the aggregate residence time; the target value is 5-10℃. S6. Safety monitoring and discharge: The gas leak detector monitors the gas concentration in real time. When the concentration is ≥10% LEL, the controller immediately cuts off the gas supply, stops the gas burner, starts the exhaust device and issues an audible and visual alarm. The aggregate is conveyed to the discharge port through the spiral mixing shaft. When the temperature verification T2 is within the range of 5-10℃, it is discharged through the discharge valve and enters the concrete mixing process. S7. Shutdown procedure: Stop feeding the feeder. After the aggregate in the preheating cylinder is emptied, first turn off the gas burner and electric heating components. Keep the hot circulation fan and drive motor running for 5 minutes. After cooling the equipment, turn it off. The controller records and saves the operating data.

[0014] In the aforementioned method for preheating aggregates at concrete mixing plants in frigid, high-altitude regions, in S2, the aggregate particle size is 5-31.5mm and the moisture content is ≤3%. A hot air pretreatment device is also provided at the feed inlet. Aggregates with a moisture content >3% are dried with hot air at 40-60℃ for 5-8 minutes until the moisture content is reduced to ≤3% before being fed into the preheating cylinder.

[0015] In the aforementioned method for preheating aggregates at concrete mixing plants in frigid, high-altitude regions, in S5, the controller uses a PID algorithm to adjust parameters, with a proportional coefficient Kp=2.5, integral time Ti=60s, and derivative time Td=15s, ensuring temperature control accuracy of ±0.5℃ and air pressure control accuracy of ±2kPa.

[0016] Compared with the prior art, this application has the following advantages: 1) High-efficiency preheating: The dual heating method, which combines electric heating components and gas heating components to form a heating unit, allows for flexible adjustment of heating power according to actual needs, and quickly increases the temperature of the preheating cylinder and the internal aggregate. The hot air circulation unit makes hot air circulate continuously in the preheating cylinder, which further improves the heat transfer efficiency and ensures that the aggregate can reach the appropriate preheating temperature in a short time. 2) Uniform heating: The mixing and conveying system uses the rotation of the spiral mixing shaft to continuously mix and move the aggregate inside the preheating cylinder, avoiding the problems of aggregate accumulation and uneven local heating, ensuring that each aggregate can fully absorb heat, and improving the quality stability of concrete. 3) Energy saving and consumption reduction: The hot air recovery device recovers and utilizes waste heat, reducing energy waste; The control unit adjusts the operating status of the device in real time based on parameters such as ambient temperature, air pressure and aggregate temperature, which avoids excessive energy consumption and reduces production costs. 4) Strong adaptability: Specifically designed for low temperature and low air pressure environments in frigid and high-altitude regions, it can operate stably under harsh conditions, meet the needs of continuous concrete production in the region, and ensure the progress and quality of engineering construction.

[0017] Therefore, this invention has the advantage of being able to be effectively applied in the unique environment of severe cold and high altitude, meeting the needs of continuous concrete production. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0019] Figure 2 This is a flowchart illustrating the method of the present invention. The markings in the attached diagram are: 1-preheating cylinder, 11-feed inlet, 12-discharge outlet, 2-drive motor, 3-spiral stirring shaft, 4-insulation layer, 5-electric heating component, 6-gas burner, 61-gas interface, 7-hot air circulation fan, 71-hot air duct, 8-hot air recovery component. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0021] Example 1. An aggregate preheating device for a concrete mixing plant in extremely cold and high-altitude areas, such as... Figure 1 As shown, the device includes a preheating cylinder 1, a heating unit, a hot air circulation unit, a conveying unit, and a control unit. The preheating cylinder 1 has a discharge port 12 at its lower left end and a feed port 11 at its upper right end. The heating unit includes a gas-fired heating assembly located at the right end of the preheating cylinder 1 and electric heating assemblies 5 distributed on the outer wall of the preheating cylinder 1. The hot air circulation unit includes a hot air circulation fan 7, a hot air duct 71, and a hot air recovery assembly 8 located at the discharge port 12. One end of the hot air duct 71 is connected to the inner side of the left end of the preheating cylinder 1, and the other end is connected to the gas-fired heating assembly. The hot air circulation fan 7 is mounted on the hot air duct 71. The inner wall of the preheating cylinder 1 is provided with an insulation layer 4.

[0022] The insulation layer 4 effectively reduces heat loss within the preheating cylinder 1.

[0023] A hot air circulation fan 7 is installed on one side of the preheating cylinder 1 and is connected to the inside of the preheating cylinder 1 through a hot air duct 71. It is used to extract the hot air in the preheating cylinder 1 and send it back into the preheating cylinder 1 to form a hot air circulation. The hot air recovery component 8 is located near the discharge port 12 of the preheating cylinder 1. It is used to recover the waste heat carried out when the aggregate is discharged and transfer the recovered heat to the cold air newly entering the preheating cylinder 1, thereby improving energy utilization. The conveying unit includes a drive motor 2 located at the left end of the preheating cylinder 1 and a spiral stirring shaft 3 horizontally inserted in the preheating cylinder 1 and connected to the output end of the drive motor 2; the spiral stirring shaft 3 includes a shaft body and spiral blades distributed on the shaft body.

[0024] The gas heating assembly includes a gas burner 6 and a gas inlet 61 for supplying gas; the air outlet of the gas burner 6 is connected to the preheating cylinder 1.

[0025] The electric heating component 5 is an electromagnetic heater.

[0026] The control unit includes a temperature sensor, a pressure sensor, a controller, and a display screen; The temperature sensors are respectively installed inside the preheating cylinder 1, at the discharge port 12 and the inlet 11, for real-time monitoring of aggregate temperature; The pressure sensor is located inside the preheating cylinder 1 and is used to monitor the internal air pressure; The controller is electrically connected to the temperature sensor, pressure sensor, heating unit, hot air circulation unit, and conveying unit, and automatically adjusts the heating power, hot air circulation speed, and stirring and conveying speed according to the signals fed back by the sensors. The display screen is installed on the control panel of the preheating cylinder 1 and is used to display the operating parameters and working status of the device, so as to facilitate the operator to monitor and adjust it.

[0027] The insulation layer 4 is a composite insulation structure, consisting of a ceramic fiber layer, an aluminum foil reflective layer, a rock wool layer, and a protective shell from the inside out. The composite insulation structure is fixed to the inner wall of the preheating cylinder 1 by a high-temperature resistant adhesive, and the protective shell is connected to the flange of the preheating cylinder 1 by bolts.

[0028] The ceramic fiber layer has a thickness of 50mm±5mm and a thermal conductivity of ≤0.03W / (m・K); the aluminum foil reflective layer has a thickness of 0.1mm and a reflectivity of ≥90%; the rock wool layer has a thickness of 80mm±5mm and a compressive strength of ≥40kPa; and the protective shell is made of 304 stainless steel with a thickness of 2mm.

[0029] The gas heating assembly also includes a gas leak detector (model JL-200, detection range 0-100% LEL, response time ≤3s), a flameout protection device (model XH-300, action time ≤0.5s), and an air ratio regulating valve (model KV-32, adjustment range 0-100%). The gas leak detector is electrically connected to the control unit and transmits leak signals in real time. The flameout protection device is linked to the gas burner 6 and automatically cuts off the gas supply when the burner is extinguished. The air ratio regulating valve is connected in series with the gas interface 61 and its opening is adjusted by the control unit.

[0030] A method for preheating aggregates in concrete mixing plants in frigid, high-altitude regions, such as... Figure 2 As shown, it includes the following steps: S1. Equipment initialization: Start the controller, temperature and pressure sensors perform self-tests, the display shows the initial parameters, and an alarm signal is issued if the sensor is abnormal. The controller is a PLC controller, model S7-1200; the temperature sensor is a PT100 type, with a measurement range of -50℃ to 100℃ and an accuracy of ±0.2℃; the pressure sensor is an MPX5700 type, with a measurement range of 0-100kPa and an accuracy of ±1kPa; and the display is a TFT LCD model LM240100 with a resolution of 800×600dpi.

[0031] S2. Aggregate conveying: The aggregate is fed into the preheating cylinder 1 through the vibrating feeder at the feed port 11. The drive motor is started, which drives the spiral stirring shaft 3 to rotate at a speed of 5-10 r / min. The aggregate moves to the left along the axis of the preheating cylinder 1. The gap between the spiral blades of the spiral stirring shaft 3 and the inner wall of the preheating cylinder 1 is maintained at 5-8 mm. The vibrating feeder model GZ-5 has a feeding capacity of 10-50t / h, a drive motor model YVP200L-4 with a power of 30kW and a frequency conversion range of 5-50Hz. S3, Heating Mode Selection: The controller selects the heating mode based on the initial aggregate temperature T0 detected by the temperature sensor at the feed inlet 11. When T0 < -20℃, activate the low-temperature mode: first start the gas burner 6, and introduce gas through gas interface 61 (DN50), with an initial gas supply of 1.0-1.2 m³ / h. 3 / h, and simultaneously start electric heating component 5, with an initial power of 50-60kW; When -20℃≤T0<-10℃, the medium temperature mode is activated: the gas burner 6 and the electric heating component 5 are activated synchronously, the gas supply is 0.7-1.0m³ / h, and the electric heating power is 40-50kW; When T0 ≥ -10℃, activate the normal temperature mode: only electric heating element 5 is activated, with a power of 30-40kW; Gas burner 6, heat load 500kW, applicable gas types: natural gas / liquefied petroleum gas; S4. Hot air circulation control: The hot air circulation fan 7 is started, and the hot air at the left end of the preheating cylinder 1 is drawn back to the input end of the gas burner 6 through the hot air pipe 71 and mixed with the newly introduced gas for combustion; the hot air recovery component 8 recovers the waste heat brought out by the aggregate at the discharge port 12, and transfers the heat to the cold air pretreatment chamber at the feed port 11 through the heat conduction pipe, preheating the cold air entering the cylinder to -5℃-0℃; Heat circulation fan, model 7, 9-19-5A, air pressure 3000-5000Pa, air volume 1500-3000m³ / h; The hot air duct is made of Q235 material, has a diameter of 300mm, and is wrapped with a polyurethane insulation layer. The hot air recovery assembly 8 includes a recovery hood, a stainless steel heat-conducting pipe, and an insulation jacket; S5. Dynamic parameter adjustment: The controller receives sensor signals in real time and dynamically adjusts the operating parameters. When the internal temperature T1 of the preheating cylinder 1 is less than 3℃, increase the gas supply by 0.1-0.2m³. 3 / h or electric heating power 5-10kW; When T1 > 12℃, reduce the gas supply by 0.1-0.2m³. 3 / h or reduce the electric heating power by 5-10kW; When the internal air pressure P of the cylinder is less than 50 kPa, adjust the opening of the air ratio regulating valve to 80-90% to maintain the air-fuel ratio at 15:1 and ensure complete combustion of the fuel. When the discharge port temperature T2 deviates from the target value by ±1℃, adjust the speed of the spiral stirring shaft 3 by ±1r / min and adjust the aggregate residence time; the target value is 5-10℃. S6. Safety monitoring and discharge: The gas leak detector monitors the gas concentration in real time. When the concentration is ≥10% LEL, the controller immediately cuts off the gas supply, stops the gas burner 6, starts the exhaust device and issues an audible and visual alarm; the aggregate is conveyed to the discharge port 12 through the spiral mixing shaft 3. When the temperature verification T2 is within the range of 5-10℃, it is discharged through the discharge valve and enters the concrete mixing process. S7. Shutdown procedure: Stop feeding the feeder. After the aggregate in the preheating cylinder 1 is emptied, first turn off the gas burner 6 and the electric heating component 5. Keep the hot circulation fan 7 and the drive motor 2 running for 5 minutes. After cooling the equipment, turn it off. The controller records and saves the operating data.

[0032] In S2, the aggregate particle size is 5-31.5mm and the moisture content is ≤3%; A hot air pretreatment device is also provided at the feed inlet 11. The aggregate with a moisture content >3% is dried with hot air at 40-60℃ for 5-8 minutes, so that the moisture content is reduced to ≤3% before being sent into the preheating cylinder 1.

[0033] In S5, the controller uses a PID algorithm for parameter adjustment, with a proportional coefficient Kp=2.5, integral time Ti=60s, and derivative time Td=15s, ensuring a temperature control accuracy of ±0.5℃ and a pressure control accuracy of ±2kPa.

[0034] Example 2. An aggregate preheating device for a concrete mixing plant in extremely cold and high-altitude areas, with results identical to those in Example 1.

[0035] The preheating cylinder is made of Q345R low-temperature pressure vessel special steel plate. The cylinder length is 6-8m, the inner diameter is 1.2-1.5m, and the wall thickness is 12-16mm. It is optimized for low-pressure working conditions at altitudes above 4000m. The cylinder ends adopt a flange sealing structure, and the sealing gasket is made of low-temperature resistant silicone rubber (working temperature -50℃ to 100℃) to ensure airtightness.

[0036] Q345R steel plate has excellent low-temperature impact toughness (impact energy ≥34J at -20℃), which can resist the risk of structural embrittlement in severe cold environments. The exterior of the cylinder is coated with an anti-corrosion coating consisting of sandblasting, epoxy zinc-rich primer, and polyurethane topcoat, with a coating thickness ≥150μm, making it suitable for corrosive environments with high altitude, strong ultraviolet radiation, and large temperature differences between day and night.

[0037] The heating unit adopts a dual-mode composite heating structure of gas heating and electric heating, which is suitable for different low-temperature working conditions and takes into account both heating speed and energy consumption control.

[0038] A method for preheating aggregates in a concrete mixing plant in frigid, high-altitude regions includes the following steps: S1. Device initialization: When the controller is started, the system automatically enters self-test mode and sequentially completes the functional tests of the temperature sensor, pressure sensor, wind speed sensor, material level sensor, and gas leak detector. The display screen shows the status of each sensor in real time. Simultaneously perform line insulation testing (test voltage 500V) and gas pipeline air tightness testing (test pressure 0.1MPa, pressure holding for 5min, pressure drop ≤0.005MPa). After the self-test passes, the display screen shows the initial parameters (ambient temperature, initial cylinder temperature, air pressure, etc.), and the equipment enters standby mode. If the self-test detects sensor failure, poor circuit insulation, or gas leakage, it will immediately issue an audible and visual alarm (alarm volume ≥85dB, light flashing frequency 1Hz) and indicate the fault location on the display screen, and prohibit the start of heating and conveying functions. S2, Aggregate Conveying: Aggregate requirements: Select continuous graded aggregates with a particle size of 5-31.5mm. After entering the site, the aggregates should be screened to remove impurities and the moisture content should be controlled at ≤3%. If the moisture content of the aggregates is >3%, start the hot air pretreatment device at the feed inlet and introduce hot air at 40-60℃ for 5-8 minutes. Monitor the moisture content in real time during the drying process and stop drying when the moisture content drops to ≤3%. Conveying operation: Start the vibrating feeder and adjust the feeding rate (10-50t / h) according to the material level sensor data to evenly feed the aggregate into the preheating cylinder; at the same time, start the drive motor to drive the spiral mixing shaft to rotate at a speed of 5-10r / min, and the aggregate moves to the left along the cylinder axis; Parameter matching: Adjust the speed of the spiral mixing shaft according to the aggregate particle size. The speed should be 8-10 r / min when the particle size is 5-16 mm and 5-7 r / min when the particle size is 16-31.5 mm to ensure that the aggregate is in full contact with the blades and is mixed evenly. The gap between the spiral blades and the inner wall of the cylinder should be maintained at 5-8 mm. Check the gap regularly (every 8 hours). If the wear causes the gap to exceed 10 mm, adjust or replace the blades in time. S3, Heating Mode Selection: The controller selects the heating mode based on the initial aggregate temperature T0 detected by the temperature sensor at the feed inlet 11. When T0 < -20℃, activate the low-temperature mode: first start the gas burner 6, and introduce gas through gas interface 61 (DN50), with an initial gas supply of 1.0-1.2 m³ / h. 3 / h, and simultaneously start electric heating component 5, with an initial power of 50-60kW; When -20℃≤T0<-10℃, the medium temperature mode is activated: the gas burner 6 and the electric heating component 5 are activated synchronously, the gas supply is 0.7-1.0m³ / h, and the electric heating power is 40-50kW; When T0 ≥ -10℃, activate the normal temperature mode: only electric heating element 5 is activated, with a power of 30-40kW; Gas burner 6, heat load 500kW, applicable gas types: natural gas / liquefied petroleum gas; S4. Hot air circulation control: The hot air circulation fan starts synchronously with the heating unit, and the initial speed is adjusted according to the heating mode: 1200-1450 r / min in low temperature mode, 1000-1200 r / min in medium temperature mode, and 960-1000 r / min in normal temperature mode. Hot air is drawn back to the gas burner input end through the hot air duct and mixed with the newly introduced gas and air for combustion. The high-temperature gas (temperature 80-100℃) after combustion re-enters the preheating cylinder to heat the aggregate. The hot air recovery component continuously recovers the waste heat from the discharge port and transfers the heat to the cold air pretreatment chamber at the inlet through a heat pipe, preheating the cold air entering the cylinder to -5℃ to 0℃ and reducing temperature shock. The wind speed sensor monitors the circulating wind speed in real time. If the wind speed is lower than 10m / s, the controller automatically increases the speed of the hot air circulation fan to ensure circulation efficiency. S5. Dynamic parameter adjustment: The controller receives sensor signals in real time and dynamically adjusts the operating parameters. When the internal temperature T1 of the preheating cylinder 1 is less than 3℃, increase the gas supply by 0.1-0.2m³. 3 / h or electric heating power 5-10kW; When T1 > 12℃, reduce the gas supply by 0.1-0.2m³. 3 / h or reduce the electric heating power by 5-10kW; for every 1000m increase in altitude, increase the temperature control target value by 0.5℃ to compensate for the thermal efficiency loss under low air pressure; When the internal air pressure P of the cylinder is less than 50 kPa, adjust the opening of the air ratio regulating valve to 80-90% to maintain the air-fuel ratio at 15:1 and ensure complete combustion of the fuel. When the discharge port temperature T2 deviates from the target value by ±1℃, adjust the speed of the spiral stirring shaft 3 by ±1r / min to adjust the aggregate residence time; the target value is 5-10℃; for every 1000m increase in altitude, increase the opening of the air ratio regulating valve by 5% to adapt to the combustion requirements in a low-oxygen environment; Residence time adjustment: The target temperature at the discharge port is 5-10℃. When the discharge port temperature T2 deviates from the target value by ±1℃, adjust the speed of the spiral stirring shaft by ±1r / min (speed range 5-10r / min) to adjust the residence time of the aggregate in the cylinder (residence time 8-20min). Gas pressure regulation: The inlet pressure is dynamically adjusted according to the gas type, with natural gas inlet pressure at 0.02-0.05MPa and liquefied petroleum gas at 0.08-0.12MPa to ensure a stable gas supply; S6. Safety monitoring and discharge: The gas leak detector monitors the gas concentration in real time. When the concentration is ≥10% LEL, the controller immediately cuts off the gas supply, stops the gas burner 6, starts the exhaust device to continuously exhaust for 15 minutes, and issues an audible and visual alarm until the gas concentration drops to <5% LEL. After the aggregate is conveyed to the discharge port by the spiral mixing shaft, the temperature sensor automatically detects T2. If T2 is within the range of 5-10℃, the discharge valve automatically opens and the aggregate enters the concrete mixing process; if T2 is below 5℃ or above 10℃, the discharge valve closes and the controller automatically adjusts the heating parameters (increasing / decreasing the amount of gas or the power of electricity) until the temperature reaches the standard. A manual inspection is conducted once per hour, using a portable thermometer (accuracy ±0.1℃) to measure the aggregate temperature at the discharge port, and comparing it with sensor data to ensure temperature accuracy; S7. Shutdown Procedure: Stop feeding the vibrating feeder, monitor the amount of aggregate in the preheating cylinder through the material level sensor, and wait until the aggregate is completely emptied (the material level sensor displays "empty cylinder") before turning off the gas burner and electric heating components. Keep the hot air circulation fan and drive motor running for 5 minutes to cool the equipment and prevent the cylinder and stirring shaft from deforming due to sudden cooling. After cooling is complete, the hot air circulation fan and drive motor are turned off, and the controller automatically records and saves the data of this operation (running time, heating mode, gas consumption, power consumption, average discharge temperature, etc.). After shutdown, perform routine checks: clean residual aggregate from the feed inlet and outlet, check the wear of the spiral blades, check for damage to the insulation layer, confirm that there are no leaks at the gas pipeline interfaces, and ensure normal operation the next time the machine is started.

[0039] In S2, the aggregate particle size is 5-31.5mm and the moisture content is ≤3%; A hot air pretreatment device is also provided at the feed inlet 11. The aggregate with a moisture content >3% is dried with hot air at 40-60℃ for 5-8 minutes, so that the moisture content is reduced to ≤3% before being sent into the preheating cylinder 1.

[0040] In S5, the controller uses a PID algorithm for parameter adjustment, with a proportional coefficient Kp=2.5, integral time Ti=60s, and derivative time Td=15s, ensuring a temperature control accuracy of ±0.5℃ and a pressure control accuracy of ±2kPa.

[0041] Installation requirements The equipment installation site must be flat, with a ground bearing capacity of ≥20kPa, and sufficient space must be reserved for equipment maintenance (≥1.5m on all sides). When installing the preheating cylinder, ensure that the horizontal error is ≤0.5mm / m, the flange connection bolts are tightened evenly, and the sealing gaskets are undamaged; Gas pipelines must be installed away from fire sources and electrical equipment. The pipeline slope must be ≥3‰. A drain valve must be installed at the lowest point. PTFE sealing tape must be used to seal the joints. An airtightness test must be conducted after installation. Electrical equipment installation must comply with high-altitude electrical specifications, the grounding system must be reliable, and cables must be made of low-temperature and UV-resistant materials. Avoid pulling or damaging them during installation. The sensor installation position must be accurate: the temperature sensor should be inserted into the cylinder to a depth of ≥100mm, avoiding contact with the aggregate or cylinder wall; the gas leak detector should be installed 0.5m below the gas interface to ensure detection sensitivity.

Claims

1. A cold high altitude concrete mixing plant aggregate preheating device, characterized in that: The application relates to a preheating cylinder (1), a heating unit, a hot air circulation unit, a conveying unit and a control unit; a discharge port (12) is arranged at the lower left end of the preheating cylinder (1), and an inlet port (11) is arranged at the upper right end of the preheating cylinder (1); the heating unit comprises a gas heating assembly arranged at the right end of the preheating cylinder (1) and an electric heating assembly (5) distributed on the outer wall of the preheating cylinder (1); the hot air circulation unit comprises a hot air circulation fan (7), a hot air pipeline (71) and a hot air recovery assembly (8) arranged at the discharge port (12); one end of the hot air pipeline (71) is connected with the inner side of the left end of the preheating cylinder (1), the other end is connected with the gas heating assembly, and the hot air circulation fan (7) is arranged on the hot air pipeline (71); and a heat preservation layer (4) is arranged on the inner wall of the preheating cylinder (1).

2. A device for preheating aggregates for a concrete mixing plant in a cold high-altitude region according to claim 1, characterized in that: The conveying unit comprises a driving motor (2) arranged at the left end of the preheating cylinder (1) and a spiral stirring shaft (3) horizontally arranged in the preheating cylinder (1) and connected with the output end of the driving motor (2).

3. A device for preheating aggregates for a concrete mixing plant in a cold high-altitude region according to claim 1, characterized in that: The gas heating assembly comprises a gas burner (6) and a gas interface (61) through which gas is supplied; and the air outlet of the gas burner (6) is communicated with the preheating cylinder (1).

4. A device for preheating aggregates for a concrete mixing plant in a cold high-altitude region according to claim 1, characterized in that: The electric heating assembly (5) is an electromagnetic heater or an electric resistance heater.

5. A device for preheating aggregates for a concrete mixing plant in a cold high-altitude region according to claim 1, characterized in that: The control unit comprises temperature sensors, pressure sensors, a controller and a display screen; The temperature sensors are arranged at the inside of the preheating cylinder (1), the discharge port (12) and the inlet port (11) respectively; The pressure sensors are arranged in the preheating cylinder (1); The controller is electrically connected with the temperature sensors, the pressure sensors, the heating unit, the hot air circulation unit and the conveying unit; The display screen is arranged on the operation panel matched with the preheating cylinder (1).

6. A cold high altitude concrete plant aggregate preheating apparatus as claimed in claim 1, wherein: The heat preservation layer (4) is a composite heat preservation structure which comprises, from inside to outside, a ceramic fiber layer, an aluminum foil reflection layer, a rock wool layer and a protective shell; the composite heat preservation structure is fixed with the inner wall of the preheating cylinder (1) through a high-temperature resistant adhesive, and the protective shell is connected with the flange of the preheating cylinder (1) through bolts.

7. A device for preheating aggregates for a concrete mixing plant in a cold high-altitude region according to claim 3, characterized in that: The gas heating assembly further comprises a gas leakage detector, a flameout protection device and an air ratio adjusting valve; the gas leakage detector is electrically connected with the control unit and transmits leakage signals in real time; the flameout protection device is linked with the gas burner (6) and automatically cuts off the gas supply when the flameout occurs; and the air ratio adjusting valve is connected with the gas interface (61) in series and the opening degree of the air ratio adjusting valve is adjusted by the control unit.

8. The method of claim 1-7, wherein the method is characterized by, The application further discloses a preheating method of the preheating device. S1, equipment initialization: starting the controller, self-checking the temperature sensors and the pressure sensors, displaying initial parameters on the display screen, and sending an alarm signal if the sensors are abnormal; S2, aggregate conveying: feeding the aggregate into the preheating cylinder (1) through the vibrating feeder of the inlet port (11), starting the driving motor, driving the spiral stirring shaft (3) to rotate at a rotating speed of 5-10 r / min, moving the aggregate along the preheating cylinder (1) in the axial direction to the left, and keeping the gap between the spiral blade of the spiral stirring shaft (3) and the inner wall of the preheating cylinder (1) at 5-8 mm; S3, heating mode selection: selecting the heating mode according to the initial temperature T0 of the aggregate detected by the temperature sensor of the inlet port (11) by the controller: When T0<-20℃, start low temperature mode: start gas burner (6) first, gas is supplied through gas interface (61), initial gas supply 1.0-1.2m 3 / h, at the same time, start electric heating assembly (5), initial power 50-60kW; When -20℃≤T0<-10℃, start the medium temperature mode: start the gas burner (6) and the electric heating assembly (5) synchronously, the gas supply amount is 0.7-1.0m³ / h, and the electric heating power is 40-50kW; When T0≥-10℃, start the normal temperature mode: only start the electric heating assembly (5), and the power is 30-40kW; S4, hot air circulation regulation: start the hot air circulation fan (7), the hot air at the left end of the preheating cylinder (1) is drawn back to the input end of the gas burner (6) through the hot air pipeline (71) and mixed with the newly-incoming gas to burn; the hot air recovery assembly (8) recovers the residual heat of the aggregate from the discharge port (12), and transmits the heat to the cold air pre-treatment cavity at the feeding port (11) through the heat conduction pipe, so that the cold air entering the cylinder is preheated to -5-0℃; S5, dynamic adjustment of parameters: the controller receives the sensor signals in real time, and dynamically adjusts the operation parameters: When the temperature T1 inside the preheating cylinder (1) is less than 3°C, increase the gas supply by 0.1-0.2 m 3 / h or the electric heating power by 5-10 kW. When T1> 12℃, reduce gas supply amount 0.1-0.2m 3 / h or reduce electric heating power 5-10kW; When the air pressure P in the cylinder is less than 50kPa, the opening degree of the air ratio adjusting valve is adjusted to 80-90%, so that the air-gas ratio is maintained at 15:1, and the gas is fully burned; When the temperature T2 at the discharge port deviates from the target value by ±1℃, the rotation speed of the spiral stirring shaft (3) is adjusted by ±1r / min, and the aggregate residence time is adjusted; the target value is 5-10℃; S6, safety monitoring and discharging: the gas leakage detector monitors the gas concentration in real time, when the concentration is greater than or equal to 10% LEL, the controller immediately cuts off the gas supply, stops the gas burner (6), starts the exhaust device and sends out sound and light alarms; the aggregate is conveyed to the discharge port (12) by the spiral stirring shaft (3), and when the temperature T2 is in the range of 5-10℃, it is discharged through the discharge valve and enters the concrete mixing process; S7, shutdown process: stop the feeder, after the aggregate in the preheating cylinder (1) is discharged, first close the gas burner (6) and the electric heating assembly (5), keep the hot air circulation fan (7) and the driving motor (2) running for 5min, then cool the equipment, record the operation data and save it by the controller.

9. A method of preheating aggregates for a cold high altitude concrete mixing plant as defined in claim 8, wherein: In S2, the aggregate particle size is 5-31.5mm, and the moisture content is less than or equal to 3%; In the feeding port (11), a hot air pre-treatment device is further arranged, the aggregate with a moisture content greater than 3% is dried by 40-60℃ hot air for 5-8min, so that the moisture content is reduced to less than or equal to 3%, and then sent into the preheating cylinder (1).

10. A method of preheating aggregates for a cold high altitude concrete mixing plant as defined in claim 8, wherein: In S5, the controller uses the PID algorithm to adjust the parameters, the proportional coefficient Kp=2.5, the integral time Ti=60s, and the differential time Td=15s, so as to ensure that the temperature control accuracy is ±0.5℃, and the air pressure control accuracy is ±2kPa.

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