Production method of recycled asphalt mixture

Abstract

The invention relates to the technical field of asphalt mixture processing and manufacturing, and discloses a recycled asphalt mixture production method which comprises the following steps: a control center receives an instruction to lock a mechanical gate, disconnects a linkage state of a primary device and a regeneration device, and establishes a single-roller operation state; the asphalt pavement milling material is put into a reclaimed material roller for single-roller direct heating; performing water vapor protection, flow field decoupling and thermal permeation anti-oxidation control on the heated regenerated material through a frequency converter and a combustor, and outputting an activated regenerated material; and discharging into a mixing cylinder for dry mixing, calculating an active power attenuation derivative to judge a thermal activation state, and generating a cross-stage feedforward correction instruction to complete continuous production. A cold air leakage path is cut off, free oxygen is blocked by water vapor, internal heat permeation conduction is switched, and high-temperature aging of old asphalt is avoided; the internal cold core is objectively recognized through electrical characteristics, the operation speed is lowered, the material heating time is prolonged, and continuous output of unqualified products is blocked.

Description

Technical Field

[0001] This invention relates to the field of asphalt mixture processing and manufacturing technology, and in particular to a method for producing recycled asphalt mixture. Background Technology

[0002] Currently, asphalt pavement recycling technology mainly adopts plant-mixed hot recycling. With the increasing environmental standards, the industry is gradually promoting the application of high-content recycled materials. In recent years, the widespread use of twin-drum mixing equipment has provided a hardware foundation for increasing the proportion of recycled materials. Conventional production schemes mainly adopt a twin-drum parallel operation mode, where virgin material is heated by the main drum and then mixed with recycled material in the mixing drum, relying on temperature zone control to process virgin material and recycled material separately.

[0003] However, existing dual-drum systems have inherent drawbacks in producing high-content recycled asphalt mixtures. When the recycled content is high, the temperature difference between the virgin and recycled materials leads to insufficient fusion and uneven coating of the old and new asphalt. Simultaneously, the synchronous operation of the two drums generates redundant power consumption, and the recycled material typically requires a separate crushing and screening pretreatment process. Especially under high-content conditions where the milled material content exceeds 55%, the virgin material system, due to insufficient feed flow, will trigger an overheating alarm and cause system interlock shutdown, disrupting continuous production. Furthermore, the virgin material system operating under no-load or low-load conditions creates cold air leakage paths, resulting in additional heat loss.

[0004] For high-component production conditions, if the equipment switches to a single-cylinder direct heating mode for a large proportion of recycled materials, the conventional continuous direct heating operation will cause high-temperature oxidation and aging of the asphalt on the surface of the old aggregate. At the same time, existing production control generally relies on external temperature measuring elements to monitor the surface temperature of the material, which cannot accurately identify the cold core structure inside the old aggregate that is not fully heated, thus leading to the continuous production of substandard mixtures and making it difficult to meet engineering quality requirements. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing recycled asphalt mixtures, which solves the problems of existing double-drum equipment in the production of recycled asphalt mixtures, such as the interlocking shutdown caused by the virgin material system being unloaded and the heat loss caused by air leakage, and the high-temperature aging of the old asphalt surface caused by continuous direct heating of the single drum. At the same time, conventional surface temperature monitoring cannot accurately identify the cold core defects remaining inside the material, thus leading to the continuous production of unqualified mixtures.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for producing recycled asphalt mixture, comprising the following steps:

[0008] The control center receives the single-drum operation mode command, outputs hardware control signals to close and lock the mechanical gate, disconnects the linkage between the virgin material equipment and the recycled material equipment, and establishes the single-drum operation mode.

[0009] In the single-drum operation state, asphalt pavement milling material that has not undergone separate crushing and screening process is fed into the feed hopper, and all the material enters the recycled material drum for single-drum direct heating to generate heated recycled material in the heating stage.

[0010] The control center uses a frequency converter module and a burner to perform water vapor protection, flow field decoupling, and heat penetration anti-oxidation control on the heated recycled material, and outputs activated recycled material that reaches the target discharge temperature;

[0011] The activated recycled material is discharged into the mixing tank for dry mixing, the active power attenuation derivative is calculated, the thermal activation state is determined, and cross-stage feedforward correction instructions are generated based on the thermal activation state results to adjust the hardware operating parameters of subsequent batches.

[0012] The continuous production of recycled asphalt mixtures is accomplished using the cross-stage feedforward correction instructions.

[0013] As a further solution, the step of the control center receiving the single-drum operation mode command, outputting a hardware control signal to close and lock the mechanical gate, disconnecting the linkage between the virgin material equipment and the recycled material equipment, and establishing the single-drum operation state specifically includes:

[0014] After receiving the single-drum operation mode command, the control center calls the preset interlocking shielding program block; runs the interlocking shielding program block, and outputs the hardware control signal by forcibly assigning the raw material flow variable in the interlocking trigger condition to a logic safety constant bypass alarm signal; uses the hardware control signal to close and lock the mechanical gate, disconnects the linkage between the raw material equipment and the recycled material equipment, and finally establishes the single-drum operation state.

[0015] As a further embodiment, the step of using the hardware control signal to close and lock the mechanical gate, thereby disconnecting the linkage between the virgin material equipment and the recycled material equipment, specifically includes:

[0016] The digital output module of the control center sends out the hardware control signal to drive the mechanical gate to perform the physical action of closing and locking; the physical action cuts off the cold air leakage path of the raw material equipment, triggering the limit switch to feed back the closed position electrical signal; the control center receives the closed position electrical signal and, in combination with the preset anti-interference delay period, confirms in the internal system that the linkage state is completely disconnected.

[0017] As a further embodiment, the step of feeding asphalt pavement milling material without separate crushing and screening into the feed hopper under the single-drum operating state, and having all material enter the recycling drum for direct heating in a single drum to generate heated recycled material in the heating stage, specifically includes:

[0018] In the single-drum operation state, the control center sends an initial command to the frequency converter module via the communication bus to set the reference operating parameters of the recycled material drum; according to the initial command, the recycled material drum is driven to feed the asphalt pavement milling material, which does not undergo a separate crushing and screening process, into the feed hopper; the fed asphalt pavement milling material then enters the recycled material drum, which rotates at the reference speed of the drum wall, for single-drum direct heating, thereby generating the heated recycled material in the heating stage.

[0019] As a further solution, in the steps of the control center performing water vapor protection, flow field decoupling, and heat penetration anti-oxidation control on the heated recycled material through the frequency converter module and burner, the specific steps of performing water vapor protection and flow field decoupling control on the heated recycled material include:

[0020] The current exhaust humidity generated by the heating of the recycled material is extracted, and it is determined that the current exhaust humidity exceeds the preset moisture protection trigger humidity threshold condition. Based on the satisfaction of the moisture protection trigger humidity threshold condition, the current exhaust humidity is substituted into the target dust removal fan operating frequency formula to calculate the frequency reduction command. The frequency reduction command is issued through the frequency converter module to actively reduce the operating frequency of the dust removal fan and appropriately increase the rotation speed of the recycled material drum, thereby completing the decoupling control of the flow field of the heated recycled material. The moisture protection trigger humidity threshold is an absolute humidity calibrated based on the local average moisture content of the recycled material.

[0021] As a further embodiment, the step of extracting the current exhaust humidity generated by heating the heated recycled material specifically includes:

[0022] An ejector-type anti-clogging sampling tube is fitted around the probe of the exhaust humidity sensor, and the ejector-type anti-clogging sampling tube is connected to the compressed air backflush circuit. The control center triggers the opening of the electromagnetic valve in the compressed air backflush circuit according to the set time rhythm, generating a high-pressure pulse backflush action for the probe. The high-pressure pulse backflush action is used to physically peel off the wet dust attached to the surface of the probe, and the current exhaust humidity generated by the heating of the heated recycled material is extracted.

[0023] As a further solution, the control center performs water vapor protection, flow field decoupling, and heat penetration anti-oxidation control on the heated recycled material through a frequency converter module and a burner. In the step of outputting activated recycled material at the target discharge temperature, the heat penetration anti-oxidation control on the heated recycled material specifically includes:

[0024] Extract the moving average filtered temperature value of the continuously sampled heated recycled material, and determine that the moving average filtered temperature value has reached a preset fire reduction trigger temperature threshold; based on the determination result of reaching the fire reduction trigger temperature threshold, call the dynamic fire power adjustment coefficient formula to calculate the attenuation ratio, and generate an attenuation control command; according to the attenuation control command, actively reduce the fire power load of the burner so that the heated recycled material reaches the target discharge temperature, and finally output the activated recycled material; wherein, the fire reduction trigger temperature threshold is a temperature parameter set according to the softening point characteristics of old asphalt.

[0025] As a further embodiment, in the step of feeding the activated recycled material into a mixing tank for dry mixing and calculating the active power attenuation derivative, the calculation of the active power attenuation derivative specifically includes:

[0026] The activated recycled material is discharged into the mixing tank for dry mixing. The control center collects the instantaneous active power within the dry mixing time window after the mixing tank motor is turned on. The instantaneous active power is substituted into the active power attenuation derivative formula for calculation, and the change in dry mixing friction resistance is converted into electrical attenuation characteristics. The electrical attenuation characteristics are obtained and used as the calculated active power attenuation derivative.

[0027] As a further embodiment, the step of calculating the active power attenuation derivative to determine the thermal activation state specifically includes the following when determining the thermal activation state:

[0028] The active power attenuation derivative obtained in the previous step is compared with a preset benchmark attenuation threshold. The current steady-state active power at the end of the dry mixing cycle is extracted and verified against the preset benchmark steady-state power upper limit to obtain a cross-validation result. When the cross-validation result is that the active power attenuation derivative is greater than or equal to the benchmark attenuation threshold and the current steady-state active power is lower than the benchmark steady-state power upper limit, the system outputs the thermal activation state result that is determined to be hot-through. If the cross-validation result does not meet the above conditions, the system determines that there is a cold core and outputs the corresponding thermal activation state result indicating the cold core. The benchmark attenuation threshold is obtained by standard dry mixing test calibration of new asphalt mixture of the same grade. The benchmark steady-state power upper limit is set as a multiple of the sum of the no-load power of the mixing cylinder and the additional power of the standard hot-through material dry mixing.

[0029] As a further embodiment, the step of generating cross-stage feedforward correction instructions for adjusting the operating parameters of subsequent batches of hardware based on the thermal activation state results specifically includes:

[0030] When the obtained thermal activation state result indicates the presence of a cold core, the active power attenuation derivative calculated in the previous step is extracted; the active power attenuation derivative associated with the thermal activation state result indicating the presence of a cold core is substituted into the reference speed feedforward correction formula to calculate and generate the updated bottom-level control boundary; the bottom-level control boundary is used as the cross-stage feedforward correction instruction to send control information to the frequency converter module to actively reduce the operating speed of the recycled material drum.

[0031] In summary, the present invention has at least one of the following beneficial technical effects:

[0032] 1. This invention uses a logic-forced assignment by calling the interlocking shielding program block and outputting a hardware control signal to close and lock the mechanical gate, thus disconnecting the linkage between the virgin material equipment and the recycled material equipment. This method eliminates interlocking shutdown faults caused by no-load operation of the virgin material system, and simultaneously cuts off the leakage path of cold air into the heating system, reducing system heat loss.

[0033] 2. This invention extracts exhaust humidity and moving average filtered temperature values, and uses these to control the frequency reduction of the induced draft fan, the speed increase of the recycled material drum, and the reduction of the burner's heat load. This control mechanism utilizes the water vapor released from the material to block free oxygen, and switches external heat radiation conduction to internal heat penetration conduction before the material reaches the target discharge temperature, thus avoiding high-temperature aging of the old asphalt surface caused by continuous direct heating of a single drum.

[0034] 3. This invention collects the instantaneous active power of the mixing cylinder in real time during the dry mixing stage and calculates the active power attenuation derivative. Utilizing the mechanism of converting changes in dry mixing frictional resistance into electrical attenuation characteristics, it determines whether a cold core exists within the material. When a cold core is detected, the system generates a cross-stage feedforward correction command to lower the baseline operating speed of the subsequent batch of recycled material drums, increasing the material's residence time for heating. This objectively identifies the cold core defect and prevents the continuous production of substandard mixtures. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the recycled asphalt mixture production system of the present invention;

[0036] Figure 2 This is a flow chart of the recycled asphalt mixture production method of the present invention;

[0037] Figure 3 This is a comparison curve of the heating process of the heated recycled material of the present invention;

[0038] Figure 4 This is a diagram showing the instantaneous active power evolution during the dry mixing stage of the mixing tank in this invention.

[0039] Figure 5 This is a comparison chart of the energy consumption of different schemes of the present invention. Detailed Implementation

[0040] See attached document Figure 1 The present invention provides a method for producing recycled asphalt mixture, the underlying hardware architecture of which includes a virgin material equipment section and a recycled material equipment section.

[0041] The virgin material equipment section includes a virgin material drum and a mechanical gate located at the feed end of the virgin material drum. The recycled material equipment section includes a recycled material drum, a feed hopper connected to the feed end of the recycled material drum, and a burner that provides a heat source for the recycled material drum.

[0042] The underlying hardware architecture includes a dust-collecting induced draft fan connected to the exhaust duct for extracting waste gas. The discharge ends of both the virgin material drum and the recycled material drum are connected to the rear-end mixing cylinder, which is driven by a side-mounted mixing cylinder motor. To achieve closed-loop production of recycled asphalt mixture, a frequency converter module is connected to the control center. The frequency converter module is electrically connected to both the drive motor of the recycled material drum and the dust-collecting induced draft fan.

[0043] An exhaust humidity sensor is installed at the exhaust duct. The sensor probe is fitted with an ejector-type anti-clogging sampling tube, which is connected to a compressed air backflushing circuit. An infrared material temperature sensor is installed at the discharge port of the recycled material drum. A high-frequency power transmitter is connected to the power supply circuit of the mixing cylinder motor. The signal outputs of the exhaust humidity sensor, infrared material temperature sensor, and high-frequency power transmitter are all connected to the signal input of the control center.

[0044] See attached document Figure 2 This invention provides a method for producing recycled asphalt mixture, comprising the following steps:

[0045] S1, the control center receives the single-drum operation mode command, shields the low flow alarm signal and high temperature alarm signal of the virgin material drum, outputs hardware control signal to close and lock the mechanical gate, disconnects the linkage between the virgin material equipment and the recycled material equipment, and establishes the single-drum operation state.

[0046] S2. In single-drum operation, asphalt pavement milling material that has not undergone separate crushing and screening processes is fed into the feed hopper. All materials enter the recycled material drum for single-drum direct heating to generate heated recycled material in the heating stage.

[0047] S3. The control center receives the exhaust humidity measured by the exhaust humidity sensor and the material temperature measured by the infrared material temperature sensor. Through the frequency converter module and the burner, it performs water vapor protection, flow field decoupling and heat penetration anti-oxidation control on the heated recycled material, and outputs activated recycled material that reaches the target discharge temperature.

[0048] S4. The activated recycled material is discharged into the mixing drum for dry mixing. During the dry mixing time window after the mixing drum motor is turned on, the control center collects the instantaneous active power through a high-frequency power transmitter, calculates the active power attenuation derivative to determine the thermal activation state, and generates cross-stage feedforward correction instructions to adjust the hardware operating parameters of subsequent batches based on the thermal activation state results. The continuous production of recycled asphalt mixture is completed by using the cross-stage feedforward correction instructions.

[0049] The technical details and control logic of each step in the above-mentioned recycled asphalt mixture production method will be explained in detail below, taking into account the underlying hardware architecture.

[0050] In this embodiment, refer to the appendix Figure 1 and attached Figure 2 To address the decoupling of system configuration and virgin aggregate equipment interlocking control, the control center receives single-drum operation mode commands through an internal execution program, converting the original dual-drum system into a pure recycled aggregate direct heating condition. To meet the continuous production requirements of high-proportion recycled asphalt mixtures and avoid system idling anomalies due to the lack of cold virgin aggregate, the underlying control architecture requires dual isolation at both the physical and software levels. The specific decoupling and configuration process described above is achieved through the following sub-steps:

[0051] S11. The control center continuously scans and acquires the operating mode selection parameters from the host computer. When a single-drum operating mode command is successfully received, the control center writes a single-drum mode switching flag into the register of its internal logic processing unit. For the configuration of the internal communication protocol of the control center and the interaction with the host computer interface, those skilled in the art can use conventional industrial Ethernet or RS485 bus communication technologies. Their signal transmission mechanisms are well-known in the field and will not be elaborated upon here.

[0052] S12. Based on the single-drum mode switching flag bit written above, the control center calls the preset interlocking shielding program block to shield the low flow alarm signal and high temperature alarm signal of the raw material drum. In the normal dual-drum continuous operation condition, the flow sensor of the raw material feeding belt and the system's total shutdown circuit are in an interlocked state. When the raw material flow rate is lower than the preset extremely low flow threshold, the system will trigger a low flow alarm signal; at the same time, since there is no cold raw aggregate in the raw material drum to absorb the heat of the burner, the system exhaust temperature will quickly exceed the limit and trigger a high temperature alarm signal.

[0053] Here, the range of the aforementioned extremely low flow rate threshold is typically calibrated based on the minimum continuous aggregate heat absorption load required for the safe operation of existing burners, generally set to 10% to 15% of the rated flow rate to prevent overheating of the cylinder wall. After invoking the interlock shielding program block, the control center disconnects the logical association between the sensor input pin associated with the raw material drum and the output terminal of the total shutdown command in the logic operation unit, bypassing the aforementioned alarm signal at the program level. By forcibly assigning the raw material flow rate variable in the interlock trigger condition to a logical safety constant (e.g., forcibly assigning it to the value corresponding to 100% of the full load flow rate), the system effectively avoids the risk of cascading shutdowns caused by a interruption in the supply of raw materials.

[0054] S13. After the alarm logic is masked at the software level, the digital output module of the control center sends a hardware control signal to the underlying actuator to close and lock the mechanical gate. Specifically, after being amplified by a relay, the hardware control signal drives the drive cylinder located at the feed end of the virgin material drum to extend, or drives the electric push rod to perform a displacement action, thereby causing the mechanical gate to close and lock. After the mechanical gate closes, it not only physically blocks the transmission channel of external virgin aggregate into the virgin material drum, but its core technical purpose is to completely cut off the cold air leakage path of the virgin material equipment, preventing unheated cold air from entering the system and thus disrupting the thermodynamic airflow field balance in the subsequent single-drum direct heating process of pure recycled material.

[0055] S14. The control center further receives the closed-position electrical signal from the limit switch installed at the end of the mechanical gate's travel. To avoid misjudgments caused by fluctuations in the electrical signal level of a single sensor, the control center's output judgment of the system status is based on multi-dimensional logic. Combining the bypass shielding status of the alarm signal at the software logic level, the confirmation of the physical locking electrical signal of the mechanical gate at the hardware level, and the judgment of signal continuity stability within a preset anti-interference delay period (as a preferred method, this delay period is set to 2 to 3 seconds), the control center confirms in the internal system that the linkage between the virgin material equipment section and the recycled material equipment section has been completely disconnected. At this point, the system officially establishes a single-drum operation state, making dual preparations for the independent heating of high-proportion milled material at the underlying hardware and logic control levels.

[0056] In this embodiment, refer to the appendix Figure 1 and attached Figure 2 Based on the single-drum operating state established by the aforementioned steps, the system enters the direct feeding and initial thermodynamic configuration process for high-proportion asphalt pavement milling material. Addressing the process bottlenecks such as localized overheating or uneven coating that are prone to occur when conventional dual-drum equipment processes high-proportion recycled materials, the feeding and initial configuration process in this embodiment is specifically elaborated through the following sub-steps:

[0057] S21. In single-drum operation, asphalt pavement milling material without separate crushing and screening is directly fed into the feed hopper. Conventional separate crushing and screening processes not only increase equipment maintenance costs but also easily cause secondary mechanical peeling of the aged asphalt film on the surface of the old aggregate at room temperature, thereby damaging the original micro-gradation structure. To avoid the aforementioned physical failures, this invention adopts a direct feeding strategy without pretreatment.

[0058] After the operator or the front-end feeding equipment pours the raw milled material into the feed hopper, since the mechanical gate is physically locked, all the material enters the recycled material drum along the only open conveying path for single-drum direct heating. For the drive structure and dynamic weighing mechanism in this material conveying path, those skilled in the art can use conventional variable frequency belt scales with closed-loop feedback function. The material conveying and metering methods are well-known technologies in the field and will not be elaborated upon here.

[0059] S22. Before the material absorbs heat on a large scale, the control center initializes the reference operating parameters to provide a stable initial flow field and mechanical operating boundary for subsequent thermodynamic evolution. Specifically, the control center writes the system's target discharge temperature into its internal logic storage area. Considering the minimum heat penetration energy required for the activation of lightweight components in the recycled asphalt and the critical temperature to avoid severe aging and embrittlement, the target discharge temperature is set to 160℃ as a preferred method, with an engineering tolerance range typically controlled between 155℃ and 165℃. Simultaneously, the control center sends initial commands to the frequency converter module via the communication bus, setting the reference speed of the drive motor of the recycled material drum to 18 r / min, and matching the initial reference operating frequency of the dust removal fan with the system's air network resistance.

[0060] Here, the aforementioned reference operating frequency is typically calibrated based on the system's no-load airflow resistance and the burner's initial ignition airflow requirements, with a preferred range of 35Hz to 40Hz. Simultaneously, the reference rotational speed is determined based on the dynamic matching of the drum diameter and the material's angle of repose; in actual operating conditions, its range is calibrated to be between 16r / min and 20r / min. The technical purpose of setting the reference rotational speed to 18r / min is to ensure that the lifting plate structure inside the recycled material drum can lift the milled material accumulated at the bottom to a suitable height and form a uniformly dense base curtain upon falling, thereby providing sufficient heat exchange surface area for the material to fully receive combustion heat radiation.

[0061] S23. As the aforementioned mechanical feeding continues and the initialization of the underlying control parameters is issued, the burner starts the basic heating mode under the command control of the control center. The pure asphalt pavement milling material inside the recycled material drum undergoes direct convection and heat conduction with the high-temperature flue gas jet injected by the burner under the action of the drum wall rotating at the reference speed and the continuous mechanical throwing action of the internal lifting plates.

[0062] Heated directly by external hot flue gas, trace amounts of free water entrained within the material evaporate, while the hardened asphalt film coating the surface of the old aggregate initially absorbs heat and softens. As the internal temperature gradient is initially established, the cold material gradually heats up inside the recycling drum, thus generating heated recycled material in the heating stage. After the physical addition of a high proportion of pure recycled material and the establishment of the basic thermal flow field are completed, the system immediately transitions to the subsequent water vapor protection and heat penetration anti-oxidation control processes based on this heated recycled material.

[0063] In this embodiment, refer to the appendix Figure 1 and attached Figure 2 The system generates heated recycled material in the heating stage based on previous steps, and then enters a dynamic frequency conversion and heat penetration anti-oxidation control process based on exhaust humidity and material temperature. Conventional heating methods, when processing pure recycled material, often cause carbonization and oxidation of the outer layer of old asphalt and incomplete penetration of the internal cold core due to continuous high-temperature heat radiation. To avoid these physical failures, the control center, in coordination with the underlying hardware, performs deep thermodynamic decoupling control. This dynamic control process is implemented through the following sub-steps:

[0064] S31. The control center receives the exhaust humidity measured by the exhaust humidity sensor. During the initial heating phase inside the recycled material drum, free moisture on the surface and inside the recycled material precipitates out upon heating, forming a high-concentration water vapor layer covering the tumbling area of ​​the material surface. This evaporated water vapor effectively isolates free oxygen in the high-temperature flue gas, providing physical anti-oxidation. To fully utilize the physical characteristics of this stage, the control center continuously checks whether the current exhaust humidity exceeds the preset water vapor protection trigger humidity threshold.

[0065] When this condition is met, the control center synchronously adjusts the operating parameters of the dust removal fan and the recycled material roller through the frequency converter module to achieve decoupled control of the air-material residence ratio flow field. Specifically, the control center actively reduces the operating frequency of the dust removal fan to slow down the internal air extraction speed and reduce the rapid loss of moisture; at the same time, it appropriately increases the rotation speed of the recycled material roller to increase the density of material curtains in the space.

[0066] Based on the aforementioned physical requirement of air-material decoupling, the system uses the target dust collector induced draft fan operating frequency formula to calculate the specific instructions issued. The target dust collector induced draft fan operating frequency formula is as follows:

[0067] ;

[0068] in, This indicates the operating frequency of the target dust removal induced draft fan, which is sent to the frequency converter module as the final instruction. This represents the reference operating frequency, as described in the initial calibration above, and its value is preferably in the range of 35Hz to 40Hz. The current exhaust humidity is displayed and is collected in real time at high frequency by an exhaust humidity sensor; This indicates the humidity threshold for triggering moisture protection, calibrated based on empirical values ​​of the average moisture content of local recycled materials, typically set to 10% to 15% absolute humidity. This is forcibly set during the system's underlying logic parameter configuration phase. Strictly greater than 0 to avoid program exceptions where the denominator approaches 0 in the above division operation; This represents the humidity response adjustment coefficient, which is determined based on the actual system's air network volume and exhaust hysteresis characteristics, and its value range is calibrated to be 0.15 to 0.25.

[0069] The technical purpose of the above calculation process is to construct negative feedback logic by introducing a humidity response adjustment coefficient, and guide the frequency converter module to smoothly reduce the frequency based on this. In this way, during the peak period of water vapor release in the system, the residence time of hot flue gas and protective water vapor in the cylinder is actively extended, thereby enhancing the convective heat transfer efficiency.

[0070] S32. In the aforementioned high-humidity and dusty flow field environment, sticky dust easily combines with condensed water vapor and condenses on the exhaust flue wall. To ensure the continuity of sensor sampling, the ejector-type anti-clogging sampling tube fitted outside the probe of the exhaust humidity sensor is connected to a compressed air backflush circuit. The control center triggers the opening of the solenoid valve in the compressed air backflush circuit according to the set time rhythm, performing a high-pressure pulse backflush action on the anti-clogging sampling tube to physically remove the wet dust adhering to the probe surface.

[0071] As moisture inside the material continues to evaporate and precipitate, the protective physical conditions created earlier gradually weaken. During this period, the control center simultaneously receives the material temperature measured by the infrared material temperature sensor.

[0072] Because the exhaust humidity sensor and the infrared material temperature sensor have different installation locations and response delays, the control center incorporates a timestamp-based data alignment mechanism in its internal logic to ensure that the temperature and humidity data used in the calculation are within the same physical operating condition time window. When the hardened asphalt on the surface of the old material begins to melt initially, continued application of strong external fire will cause the asphalt to oxidize rapidly. To avoid misjudgments caused by instantaneous extreme values ​​from a single sensor, the control center extracts the moving average filtered temperature values ​​from multiple consecutive sampling periods for multi-dimensional judgment. Based on the principles of heat penetration and fire reduction to prevent oxidation, when the current material temperature after filtering reaches the preset fire reduction trigger temperature threshold, the control center outputs a decay control command to the burner to actively reduce the fire load.

[0073] In this control logic, the control center uses a dynamic firepower adjustment coefficient formula to calculate the attenuation ratio of the burner's fuel or gas valve opening. The dynamic firepower adjustment coefficient formula is as follows:

[0074] ;

[0075] in, This represents the dynamic firepower adjustment coefficient, which is used as a digital output command to limit the current burner's output power. This represents the maximum value function, whose physical purpose in the program is to build the underlying limiting logic for hardware anti-flameout, preventing the output command from completely closing the valve and causing a flameout fault; This represents the minimum sustaining combustion coefficient, used to ensure stable operation of the burner under low loads; its value is set between 0.2 and 0.3. This represents the temperature penetration damping factor, the value of which is determined based on calibration experiments of the hysteresis of the thermal conductivity of old asphalt, and is preferably calibrated to 0.8. This represents the current material temperature; the input value is the effective steady-state value after the above moving average filtering process. This indicates the threshold temperature for triggering the fire, which is usually set to 110°C to 120°C based on the softening point characteristics of old asphalt. This indicates the target discharge temperature, typically set to 160℃. The system strictly limits this in the parameter verification module. Must be greater than Furthermore, the difference between the two is no less than 20°C, to ensure that the denominator in the formula is always a positive number with sufficient calculation accuracy.

[0076] As a preferred method, the physical significance of this dynamic heat regulation coefficient is that as the actual material temperature approaches the discharge target value, the system actively weakens the intensity of intense external heat radiation, forcing the heating process to enter the heat penetration stage that relies on the temperature difference between the inside and outside of the material for slow internal conduction, thereby preventing the high-temperature carbonization of the asphalt components on the aggregate surface from the root.

[0077] S33. The system maintains a heat preservation and activation state according to the above dynamic instructions. Under the condition that the heat is strictly limited by the dynamic heat adjustment coefficient, the heated recycled material continues to mechanically tumble inside the recycled material drum. External heat penetrates into the cold core inside the old aggregate in a gentle gradient, causing the hardened asphalt film to fully soften and peel off without secondary oxidation failure.

[0078] The control center continuously monitors the actual material temperature in the discharge area using an infrared material temperature sensor. When the measured material temperature stably reaches the set target discharge temperature, and the temperature fluctuation within the continuous sampling period is within the anti-interference dead zone, the system determines that the single-cylinder direct heating and thermal activation process for the current batch is complete. Subsequently, the system outputs activated recycled material that has reached the target discharge temperature. At this point, the complete thermodynamic transformation of the heated recycled material by the control center through the frequency converter module and burner, including water vapor protection, flow field decoupling, and thermal penetration anti-oxidation control, is completed. The output activated recycled material is immediately discharged into the mixing tank for the subsequent dry mixing process.

[0079] In this embodiment, refer to the appendix Figure 1 and attached Figure 2 After the aforementioned flow field decoupling and heat penetration anti-oxidation control, the system completed the single-cylinder direct heating process and then entered the thermal activation judgment and cross-stage feedforward compensation control process based on the active power attenuation derivative. Conventional heating effect judgment often relies solely on the surface temperature of the drum outlet, which easily masks the cold core defects remaining inside the old aggregate due to heat conduction hindrance. To overcome this monitoring limitation, the control center infers the physical rheological state inside the material by acquiring the dynamic electrical response of the mechanical load. This control process is specifically carried out through the following sub-steps:

[0080] S41. The system discharges activated recycled material into the mixing drum for dry mixing. Upon entering this process, the binder in the old asphalt softens due to heat and redistributes under the mechanical shear force of dry mixing to provide lubrication. Based on this rheological characteristic, the control center collects instantaneous active power via a high-frequency power transmitter within the dry mixing time window after the mixing drum motor is turned on. Instantaneous active power is chosen as the core monitoring indicator because this parameter directly reflects the macroscopic mechanical shear resistance of the aggregate-asphalt mixture as rheological viscosity changes within the mixing drum. If there are insufficiently heated cold cores within the material, the high friction between aggregates will cause the mixing drum motor to operate under consistently high loads; conversely, if the material is thoroughly heated, its mechanical shear resistance will decrease significantly, and the corresponding instantaneous active power will also show a significant decrease as the dry mixing time progresses. To quantify these physical phenomena, the control center calculates the active power decay derivative to determine the thermal activation state.

[0081] When extracting this electrical characteristic, the system uses the active power attenuation derivative formula for calculation. The active power attenuation derivative formula is as follows:

[0082] ;

[0083] in, It represents the active power decay derivative, used to characterize the average rate of decrease in electrical load during dry mixing; Indicates the current sampled active power; This indicates the active power of the previous sample; This represents the number of consecutive sampling periods. To filter out high-frequency power grid noise and prevent the denominator from approaching 0 in division operations and causing program exceptions, it is usually fixed to a positive integer between 50 and 100. This indicates the time interval between single samplings, which is calibrated according to the hardware communication baud rate of the high-frequency power transmitter and is usually set to 0.05 seconds. This indicates a summation operation.

[0084] Through the above calculations, the system successfully transforms the mechanical dimension of dry-mixing frictional resistance changes into digitally quantifiable electrical attenuation characteristics, thus providing an objective basis for subsequent identification of the internal cold core, independent of surface temperature.

[0085] S42. After obtaining the above dynamic derivative, the control center executes the thermal activation and cold core determination logic based on multi-dimensional feature comparison. To avoid misjudgment caused by transient fluctuations in the power grid due to relying solely on a single derivative extreme value, the system establishes a dual verification mechanism.

[0086] Specifically, the control center compares the calculated active power attenuation derivative with a preset benchmark attenuation threshold. Simultaneously, it extracts the current steady-state active power at the end of the dry-mixing cycle (typically the moving average of the last 3 to 5 seconds) and cross-validates it with a preset benchmark steady-state power upper limit. Both the benchmark attenuation threshold and the benchmark steady-state power upper limit are obtained through standard dry-mixing tests of new asphalt mixtures of the same grade. The benchmark steady-state power upper limit is set to 1.1 times the sum of the unloaded power of the mixing drum and the additional power of the standard hot-drying aggregate during dry mixing.

[0087] When the comparison result shows that the active power attenuation derivative is greater than or equal to the benchmark attenuation threshold, and the current steady-state active power is lower than the benchmark steady-state power upper limit, it indicates that the old asphalt on the aggregate surface has been sufficiently softened and there is no hard structure inside. The system then generates and outputs a result indicating a fully heated and activated state. If any of the above conditions are not met, i.e., the active power attenuation derivative is less than the benchmark attenuation threshold, or the current steady-state active power is greater than or equal to the benchmark steady-state power upper limit, it means that the load decrease is slow or the residual shear resistance is too large. The system then determines that a cold core exists and outputs the corresponding result indicating a heated and activated state.

[0088] S43. Based on the above determination, the system generates cross-stage feedforward correction instructions to adjust the hardware operating parameters of subsequent batches according to the thermal activation state results. Given that the current batch of material is already in the dry mixing stage, secondary reheating is physically infeasible. To prevent the continuous production of defective products, the control center implements cross-process stage feedforward compensation: when the thermal activation state results indicate the presence of a cold core, the control center actively reduces the operating speed of the recycled material roller by issuing a command to the frequency converter module, thereby extending the residence time of subsequent materials in the hot air flow field.

[0089] In this feedforward compensation logic, the control center uses the reference speed feedforward correction formula to calculate the updated underlying control boundary. The reference speed feedforward correction formula is as follows:

[0090] ;

[0091] in, This indicates the reference speed for the next batch, and the digital value of the cross-stage feedforward correction command overrides the original setting in the inverter module. This indicates the reference speed for the current batch. Its actual value is limited by the operating characteristics of the drum machinery and is usually between 16 r / min and 20 r / min. This represents the baseline attenuation threshold, which is forcibly verified to be strictly greater than 0 during system initial configuration to ensure that the denominator of the division operation has physical meaning and does not cause overflow or crash. This represents the active power attenuation derivative, and the value substituted is the electrical attenuation characteristic actually obtained from the calculation in the previous step; This represents the speed adjustment compensation coefficient, which is preferably between 0.1 and 0.2, in order to smooth the adjustment range of the mechanical hardware and prevent the internal material curtain from collapsing due to a sudden drop in speed.

[0092] As a preferred approach, by implementing the aforementioned cross-stage feedforward correction, the system successfully and dynamically adaptively adjusted the operating baseline of the front-end equipment. Ultimately, the control center used the cross-stage feedforward correction command to complete the continuous production of recycled asphalt mixture. This closed-loop control strategy transforms the a posteriori results of the physical rheological state into the basis for correcting the front-end heating flow field, completely cutting off the continuous production path of batches of cold-core defective products.

[0093] To further aid in understanding the technical solution of this invention, the following provides an embodiment and its experimental verification comparison in conjunction with a specific production application scenario, and discusses the technical effects of this invention based on experimental data.

[0094] In a maintenance project for a road with low quality requirements, the project mandated the complete utilization of waste asphalt pavement milling material for the production of recycled asphalt mixture. Operators input a single-drum operation mode command through the control center. The system then immediately severed the associated loops of the extremely low flow alarm signal and high temperature alarm signal related to the raw material drum in its underlying logic, and forcibly assigned the raw material flow parameter to a full-load state to bypass the shutdown logic.

[0095] Subsequently, the system-driven cylinder closes and locks the mechanical gate at the feed end of the virgin material drum, physically blocking the path of cold air leakage. The front-end loading equipment directly pours the milled asphalt pavement material, which has not undergone crushing and screening pretreatment, into the feed hopper, and all the material enters the recycled material drum. The system is set to a target discharge temperature of 160℃, an initial frequency of 38Hz for the dust removal fan, and a base rotation speed of 18r / min for the recycled material drum.

[0096] After the burner is turned on, the control center collects the exhaust humidity in real time. When the exhaust humidity exceeds the trigger threshold of 12%, the system dynamically adjusts the induced draft fan frequency and appropriately increases the drum speed according to the formula, retaining high-concentration water vapor inside the drum to form a physical anti-oxidation layer. When the infrared sensor detects that the material temperature reaches 115℃, the control center calculates the dynamic firepower adjustment coefficient and forcibly reduces the burner valve opening, allowing the old material to slowly undergo thermal penetration due to the temperature difference between the inside and outside. After the activated recycled material is discharged into the mixing tank, the high-frequency power transmitter collects the instantaneous active power of the mixing tank motor in real time.

[0097] The system calculates the active power attenuation derivative over 50 consecutive sampling cycles. When it is determined that there is residual cold core causing slow attenuation, the system generates a cross-stage feedforward correction instruction according to the formula, reducing the drum reference speed of the next batch to 16.5 r / min to extend the heating residence time, and finally completing the continuous closed-loop production of 100% recycled material.

[0098] To verify the actual operational effectiveness of this solution, a traditional dual-drum continuous operation was set up as a comparison under the same hardware platform and the same batch of recycled materials. In the traditional comparative model, due to the limited supply of virgin materials and the large temperature difference, the maximum amount of recycled materials was forcibly limited to 45%, and the burner adopted a constant load surface strong fire direct heating mode, lacking an electrical negative feedback correction mechanism for the dry mixing stage.

[0099] The conclusions are as follows:

[0100] See attached document Figure 3 As can be observed from the figure, the dark gray dashed line represents the temperature response of the traditional comparative model under constant high-intensity heating. Its temperature rise rate is extremely rapid, exceeding the safety threshold of 160℃ in the later stages. This rapid surface heat absorption easily leads to carbonization and severe aging of the old asphalt film. In contrast, the black solid line represents the temperature evolution trajectory of the embodiment of this invention. Relying on water vapor protection and a dynamic firepower adjustment mechanism, when the temperature reaches the preset fire-retardation trigger threshold, the system actively intervenes at the combustion boundary. The black solid line shows a significant slope decrease and eventually smoothly approaches the target temperature of 160℃. This data demonstrates that the flow field decoupling and anti-oxidation control of this invention effectively extend the time window for heat conduction to the interior, ensuring deep heat penetration of the old material while avoiding surface aging.

[0101] See attached document Figure 4This figure reflects the correspondence between the physical rheological state of materials and their electrical response. The dark gray dashed line represents the power change in the traditional comparative model. Due to the presence of insufficiently heated cold core defects, the residual high mechanical shear resistance between aggregates results in a very small derivative of active power attenuation, and the material fluctuates in a high-load steady state in the later stages. The black solid line represents the power change in the embodiment of this invention. Thanks to the dynamic adaptive adjustment of the drum rotation speed by the cross-stage feedforward correction command, the material is fully thermally activated, and the softened asphalt fully utilizes its lubricating properties. The black solid line shows a rapid decline with a large gradient in the early stage of dry mixing, and quickly converges to a stable state below the benchmark upper limit, completely cutting off the continuous production path of batches of defective cold core products, confirming the accuracy and reliability of the dual verification mechanism in identifying the thermal activation state.

[0102] See attached document Figure 5 The bar chart visually quantifies the energy consumption difference before and after hardware decoupling. The dark gray bar chart represents the basic energy consumption of the traditional comparative model under dual-drum synchronous operation, reaching as high as 235.0 kW·h. This high energy consumption mainly stems from the unavoidable idle operation of the virgin material system and air leakage in the ventilation network when processing high proportions of recycled material. The black bar chart represents the energy consumption level of the embodiment of this invention, reduced to 160.5 kW·h, saving approximately 31.2% of energy. By physically disconnecting the virgin material system from the control center and bypassing the interlocking alarm program, coupled with the complete closure of the air leakage path by the mechanical gate, this solution eliminates the ineffective power output and heat loss of non-working components, breaking through the energy consumption bottleneck of high-dosage regeneration under existing processes.

Claims

1. A method for producing recycled asphalt mixture, characterized in that, Includes the following steps: The control center receives the single-drum operation mode command, outputs hardware control signals to close and lock the mechanical gate, disconnects the linkage between the virgin material equipment and the recycled material equipment, and establishes the single-drum operation mode. In the single-drum operation state, asphalt pavement milling material that has not undergone separate crushing and screening process is fed into the feed hopper, and all the material enters the recycled material drum for single-drum direct heating to generate heated recycled material in the heating stage. The control center uses a frequency converter module and a burner to perform water vapor protection, flow field decoupling, and heat penetration anti-oxidation control on the heated recycled material, and outputs activated recycled material that reaches the target discharge temperature; The activated recycled material is discharged into the mixing tank for dry mixing, the active power attenuation derivative is calculated, the thermal activation state is determined, and cross-stage feedforward correction instructions are generated based on the thermal activation state results to adjust the hardware operating parameters of subsequent batches. The continuous production of recycled asphalt mixtures is accomplished using the cross-stage feedforward correction instructions.

2. The method for producing recycled asphalt mixture according to claim 1, characterized in that, The steps of receiving the single-drum operation mode command, outputting hardware control signals to close and lock the mechanical gate, disconnecting the linkage between the virgin material equipment and the recycled material equipment, and establishing the single-drum operation state specifically include: After receiving the single-drum operation mode command, the control center calls the preset interlocking shielding program block; The interlocking shielding program block is run, and the hardware control signal is output by forcibly assigning the raw material flow variable in the interlocking trigger condition to a logical safety constant bypass alarm signal. The mechanical gate is closed and locked using the hardware control signal, disconnecting the linkage between the virgin material equipment and the recycled material equipment, and finally establishing the single-drum operating state.

3. The method for producing recycled asphalt mixture according to claim 2, characterized in that, The step of closing and locking the mechanical gate using the hardware control signal to disconnect the linkage between the virgin material equipment section and the recycled material equipment section specifically includes: The digital output module of the control center sends out the hardware control signal, which drives the mechanical gate to perform the physical action of closing and locking. The physical action cuts off the cold air leakage path of the raw material equipment, triggering the limit switch to provide a feedback signal indicating that it is closed in place. The control center receives the closed-position electrical signal and, in conjunction with a preset anti-interference delay period, confirms in the internal system that the linkage state is completely disconnected.

4. The method for producing recycled asphalt mixture according to claim 1, characterized in that, In the single-drum operation state, the process of feeding milled asphalt pavement material without separate crushing and screening into the feed hopper, and having all the material enter the recycling drum for direct heating in a single drum to generate heated recycled material in the heating stage, specifically includes: In the single-drum operation state, the control center sends an initial command to the frequency converter module via the communication bus to set the reference operating parameters of the recycled material drum; The recycled material roller is driven according to the initial command to feed the asphalt pavement milling material, which has not undergone a separate crushing and screening process, into the feed hopper; The asphalt pavement milling material is fed into the recycled material drum, which rotates at a reference speed on the drum wall, and is then directly heated in a single drum to generate the heated recycled material in the heating stage.

5. The method for producing recycled asphalt mixture according to claim 1, characterized in that, In the steps of the control center performing water vapor protection, flow field decoupling, and heat penetration anti-oxidation control on the heated recycled material through the frequency converter module and burner, the specific steps of performing water vapor protection and flow field decoupling control on the heated recycled material include: Extract the current exhaust humidity generated by heating the heated recycled material, and determine whether the current exhaust humidity meets the preset moisture protection trigger humidity threshold condition; Based on meeting the moisture protection trigger humidity threshold condition, the current exhaust humidity is substituted into the target dust removal induced draft fan operating frequency formula to calculate the frequency reduction command; The frequency reduction command is issued by the frequency converter module to actively reduce the operating frequency of the dust removal fan and appropriately increase the speed of the recycled material drum, thereby completing the decoupling control of the flow field of the heated recycled material. The moisture protection trigger humidity threshold is an absolute humidity value calibrated based on the empirical value of the average moisture content of local recycled materials.

6. A method for producing recycled asphalt mixture according to claim 5, characterized in that, The step of extracting the current exhaust humidity generated by heating the recycled material specifically includes: An ejector-type anti-clogging sampling tube is fitted over the probe of the exhaust humidity sensor, and the ejector-type anti-clogging sampling tube is connected to the compressed air backflush circuit. The control center triggers the opening of the solenoid valve in the compressed air backflush circuit according to the set time rhythm, generating a high-pressure pulse backflush action for the probe; The high-pressure pulse backflushing action physically removes the wet dust adhering to the probe surface, and the current exhaust humidity generated by the heating of the heated recycled material is extracted.

7. The method for producing recycled asphalt mixture according to claim 1, characterized in that, In the process of the control center performing water vapor protection, flow field decoupling, and heat penetration anti-oxidation control on the heated recycled material through the frequency converter module and the burner, and outputting activated recycled material that reaches the target discharge temperature, the specific steps of performing heat penetration anti-oxidation control on the heated recycled material include: Extract the moving average filtered temperature value of the continuously sampled heated recycled material, and determine that the moving average filtered temperature value has reached the preset deflation trigger temperature threshold. Based on the determination result of reaching the fire reduction trigger temperature threshold, the attenuation ratio is calculated by calling the dynamic fire power adjustment coefficient formula, and an attenuation control command is generated. According to the attenuation control command, the fire load of the burner is actively reduced so that the heated recycled material reaches the target discharge temperature, and finally the activated recycled material is output. The fire-triggering temperature threshold is a temperature parameter set based on the softening point characteristics of old asphalt.

8. The method for producing recycled asphalt mixture according to claim 1, characterized in that, In the step of dry mixing the activated recycled material into a mixing tank and calculating the active power attenuation derivative, the specific steps include: The activated recycled material is discharged into the mixing tank for dry mixing, and the control center collects the instantaneous active power within the dry mixing time window after the mixing tank motor is turned on. The instantaneous active power is substituted into the active power attenuation derivative formula for calculation, and the change in dry-mixing friction resistance is transformed into electrical attenuation characteristics. The electrical attenuation characteristics are obtained and used as the active power attenuation derivative calculated from the electrical attenuation characteristics.

9. A method for producing recycled asphalt mixture according to claim 8, characterized in that, The step of calculating the active power attenuation derivative to determine the thermal activation state specifically includes the following steps: The active power attenuation derivative obtained in the previous step is compared with the preset reference attenuation threshold. The current steady-state active power at the end of the dry mixing cycle is extracted and verified with the preset reference steady-state power upper limit to obtain the cross-validation results. When the cross-validation result is that the active power attenuation derivative is greater than or equal to the reference attenuation threshold and the current steady-state active power is lower than the reference steady-state power upper limit, the system outputs the result of the thermal activation state that is determined to be fully heated. If the cross-validation result does not meet the above conditions, the system determines that a cold core exists and outputs the corresponding thermal activation state result indicating the cold core; The benchmark attenuation threshold is obtained through standard dry-mix test of new asphalt mixture of the same grade; the benchmark steady-state power upper limit is set as a multiple of the sum of the no-load power of the mixing cylinder and the additional power of the standard hot-through material dry mixing.

10. A method for producing recycled asphalt mixture according to claim 9, characterized in that, The step of generating cross-stage feedforward correction instructions for adjusting the operating parameters of subsequent batches of hardware based on the thermal activation state results specifically includes: When the obtained thermal activation state result indicates the presence of a cold core, the active power attenuation derivative calculated in the previous step is extracted. Substitute the active power attenuation derivative associated with the thermal activation state result indicating the presence of a cold core into the reference speed feedforward correction formula to calculate and generate the updated underlying control boundary. The underlying control boundary is used as the cross-stage feedforward correction command to send control information to the frequency converter module to actively reduce the operating speed of the recycled material drum.

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