A control method for a low speed drying tower

Abstract

The application provides a control method of a low-speed drying tower, the low-speed drying tower comprising a tower body, the tower body comprising an air inlet section, a material feeding section and a drying section arranged in an axial direction; the air inlet section being communicated with a hot air device and internally provided with a hot air speed reduction mechanism; a plurality of material nozzles being arranged in a circumferential direction in the material feeding section, the plurality of material nozzles being communicated with an external feeding device and each being individually controllable; a cold air jacket being sleeved on a side wall of the air inlet section, the cold air jacket being communicated with a cold air device; the control method comprising: acquiring a feeding quality and a discharging quality in real time, calculating an actual output rate according to the feeding quality and the discharging quality; when the actual output rate is lower than a lower limit of a target output rate, adjusting at least one of the hot air device, the cold air device and the feeding device according to a difference between the actual output rate and the lower limit of the target output rate; repeating the above adjustment step until the actual output rate meets a target output rate range. The method provided by the application can realize closed-loop feedback control and accurate adjustment to stabilize the output rate.

Description

Technical Field

[0001] This invention belongs to the field of material drying technology, specifically relating to a control method for a low-speed drying tower. Background Technology

[0002] In industries such as chemical, food, and pharmaceutical, drying technology is one of the key factors affecting the final quality of products and production efficiency. For high-viscosity materials, due to their poor flowability and tendency to adhere, the drying process places higher demands on parameters such as the uniformity of feed, hot air distribution, and residence time of the equipment. Spray drying towers and similar equipment are commonly used in the industry for this purpose.

[0003] Existing drying towers mostly employ a top-mounted structure for both air and material intake. The high velocity of the hot air entering the tower means that insufficiently dried, high-viscosity materials are easily carried into the exhaust system by the high-speed hot air, resulting in insufficient residence time within the tower, incomplete drying, and reduced effective yield. Furthermore, traditional control methods rely on fixed parameters, lacking real-time feedback and dynamic adjustment of the drying effect. This makes it difficult to adapt to fluctuations in material properties, further exacerbating material entrainment losses and unstable drying performance. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, a control method for a low-speed drying tower is provided. The low-speed drying tower includes a tower body, which includes an air inlet section, a feeding section, and a drying section arranged axially. The top of the air inlet section is connected to a hot air device, and a hot air deceleration mechanism is provided inside the air inlet section. Multiple material nozzles are arranged circumferentially inside the feeding section, and the multiple material nozzles are connected to an external feeding device, and each material nozzle is individually controllable. A cold air jacket is fitted on the side wall of the air inlet section, and the cold air jacket is connected to a cold air device. The control method includes: During the operation of the drying tower, the feed quality and discharge quality are acquired in real time, and the actual output rate is calculated based on the feed quality and discharge quality. The actual output rate is compared with the target output rate range to determine whether the actual output rate deviates from the target. When the actual output rate is lower than the lower limit of the target output rate, at least one of the hot air equipment, cold air equipment and feeding equipment shall be adjusted according to the difference between the actual output rate and the lower limit of the target output rate. Repeat the above adjustment steps until the actual output rate stabilizes within the target output rate range.

[0005] According to the technical solution provided by the present invention, while acquiring the feed quality and discharge quality in real time, the wall temperature of the drying section is also acquired. The adjustment of at least one of the hot air equipment, cold air equipment, and feeding equipment based on the difference between the actual output rate and the lower limit of the target output rate includes: The wall temperature is compared with a preset safe temperature range; When the wall temperature is greater than or equal to the upper limit of the safe temperature, obtain a first output rate deviation value calculated based on the actual output rate and the lower limit of the target output rate, and a first temperature deviation value calculated based on the wall temperature and the upper limit of the safe temperature. Based on the ratio of the first output deviation value to the first temperature deviation value, the main control deviation type of the current working condition is determined, and the adjustment center between the hot air temperature and the cold air temperature is allocated according to the main control deviation type. Based on the aforementioned adjustment of the center of gravity, coupled adjustment of reducing hot air temperature and reducing cold air temperature is performed simultaneously.

[0006] According to the technical solution provided by the present invention, the main control deviation type of the current operating condition is determined based on the ratio of the first output deviation value to the first temperature deviation value, and the adjustment center between the hot air temperature and the cold air temperature is allocated according to the main control deviation type, including: The first ratio is calculated based on the proportional relationship between the first output rate deviation value and the first temperature deviation value. When the first ratio is greater than or equal to the first preset threshold, the adjustment focus will be allocated to hot air temperature adjustment; When the first ratio is less than or equal to the second preset threshold, the adjustment focus will be allocated to the cold air temperature adjustment; When the first ratio is less than the first preset threshold and greater than the second preset threshold, the proportion of hot air temperature adjustment step size and the proportion of cold air temperature adjustment step size are determined by nonlinear mapping based on the first ratio, wherein the proportion of hot air temperature adjustment step size is negatively correlated with the first ratio and the proportion of cold air temperature adjustment step size is positively correlated with the first ratio. The hot air temperature adjustment amount is determined based on the proportion of the hot air temperature adjustment step size, and the cold air temperature adjustment amount is determined based on the proportion of the cold air temperature adjustment step size.

[0007] According to the technical solution provided by the present invention, after comparing the wall temperature with a preset safe temperature range, the method further includes: When the wall temperature is lower than the preset safe lower limit, a first output rate deviation value calculated based on the actual output rate and the target output rate lower limit, and a second temperature deviation value calculated based on the wall temperature and the safe lower limit are obtained. Based on the ratio of the first output deviation value to the second temperature deviation value, the main control deviation type of the current working condition is determined, and the adjustment center between the hot air temperature and the cold air temperature is allocated according to the main control deviation type. Based on the aforementioned adjustment of the center of gravity, coupled adjustment of increasing hot air temperature and increasing cold air temperature is performed simultaneously.

[0008] According to the technical solution provided by the present invention, after comparing the wall temperature with a preset safe temperature range, the method further includes: When the wall temperature is greater than or equal to the lower limit of the safe temperature and less than the upper limit of the safe temperature, obtain the first output rate deviation value calculated based on the actual output rate and the lower limit of the target output rate; Calculate the target feed increment based on the first output deviation value and increase the feeding rate of the feeding equipment.

[0009] According to the technical solution provided by the present invention, before increasing the feeding rate of the feeding device, the method further includes: Obtain the current open / closed status of each material nozzle; When there are material nozzles in the closed state, the number of nozzles that need to be opened is calculated based on the target feed increment, and the material nozzles in the closed state are opened sequentially according to the preset polling order. Once all material nozzles are open, increase the feeding rate of the feeding equipment.

[0010] According to the technical solution provided by the present invention, after determining whether the actual output rate deviates from the target, the method further includes: When the actual output rate is higher than the upper limit of the target output rate, the actual humidity of the discharged material is obtained; When the actual humidity is greater than or equal to the preset humidity threshold and the wall temperature is within the safe temperature range, the number of material nozzles currently in the open state is obtained, and the target number of nozzles to be closed is calculated based on the difference between the actual output rate and the upper limit of the target output rate. According to the preset polling order, the target number of material nozzles to be shut down is turned off.

[0011] According to the technical solution provided by the present invention, after performing the coupled adjustment operation of reducing the hot air temperature and reducing the cold air temperature simultaneously based on the adjustment center of gravity, the method further includes: Real-time monitoring of the rate of change of the wall temperature in the drying section; When the rate of change of the wall temperature exceeds the preset rate of change threshold, the hot air temperature adjustment amount or cold air temperature adjustment amount is reduced according to the preset ratio, and the adjustment operation is re-executed.

[0012] According to the technical solution provided by the present invention, after increasing the feeding rate of the feeding device, the method further includes: The system monitors the feeding status of each material nozzle in real time. When the feeding flow rate of any material nozzle is found to be lower than the preset lower limit, it is determined that the nozzle is blocked. Get the number of material nozzles that are currently closed; When there is a material nozzle that is closed, open one of the closed material nozzles according to the preset polling sequence, and close the material nozzle that is blocked.

[0013] According to the technical solution provided by the present invention, after sequentially opening the material nozzles that are in the closed state according to a preset polling order, the method further includes: Real-time monitoring of the feeding status of newly opened material nozzles; When the feed flow rate of the newly opened material nozzle is lower than the preset lower limit, the newly opened material nozzle is marked as faulty, and the next material nozzle in the closed state is selected to be opened according to the preset polling order.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: by axially arranging the air inlet section, the feeding section, and the drying section in sequence, a stable structural foundation is provided for the orderly contact between hot air and high-viscosity materials; the top of the air inlet section is connected to the hot air equipment and is equipped with a hot air deceleration mechanism, which can effectively reduce the hot air velocity, extend the residence time of materials in the tower, and prevent insufficiently dried materials from being carried into the exhaust system by the high-speed airflow, thereby improving the thoroughness of drying and the effective yield; multiple individually controllable material nozzles are arranged circumferentially in the feeding section, which not only realizes the uniform mixing of materials and hot air, but also provides a reliable basis for the flexible adjustment of the feed rate; the cold air jacket sleeved on the side wall of the air inlet section can actively cool the key areas of the tower, effectively preventing high-viscosity materials from gelatinizing or sticking to the wall due to local overheating. Based on this, by acquiring and dynamically comparing the actual output rate of feed and output quality in real time, closed-loop feedback control of the drying effect is achieved, overcoming the shortcomings of existing technologies that are difficult to adapt to fluctuations in material characteristics due to fixed parameter operation. When the actual output rate is lower than the target lower limit, at least one of the hot air equipment, cold air equipment, and feeding equipment is selectively adjusted, which can accurately respond to different causes of insufficient output, avoid blind adjustment leading to instability of drying conditions, and further ensure the stability of the drying process and product quality. Attached Figure Description

[0015] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the low-speed drying tower provided in this application; Figure 2 A flowchart illustrating the steps of the low-speed drying tower control method provided in this application.

[0016] The text labels in the diagram represent: 1. Air inlet section; 2. Feeding section; 3. Drying section; 4. Hot air deceleration mechanism; 5. Material nozzle; 6. Cold air jacket. Detailed Implementation

[0017] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] As mentioned in the background section, please refer to the relevant technical issues. Figure 1 and Figure 2 This embodiment proposes a control method for a low-speed drying tower. The method is based on a low-speed drying tower with a specific structure. The low-speed drying tower includes a tower body, which includes an air inlet section 1, a feeding section 2, and a drying section 3 arranged axially. The top of the air inlet section 1 is connected to a hot air device, and a hot air deceleration mechanism 4 is provided inside the air inlet section 1. Multiple material nozzles 5 are arranged circumferentially inside the feeding section 2. The multiple material nozzles 5 are connected to an external feeding device, and each material nozzle 5 is individually controllable. A cold air jacket 6 is fitted on the side wall of the air inlet section 1, and the cold air jacket 6 is connected to a cold air device.

[0020] Specifically, such as Figure 1As shown, the low-speed drying tower includes a tower body, with an air inlet section 1, a feeding section 2, and a drying section 3 arranged sequentially along the axial direction. A hot air device is connected to the top of the air inlet section 1 to supply the hot air required for drying into the tower body. The hot air device can be a combination of a filter, a fan, and a heater, and the drying process is controlled by adjusting the hot air temperature. A hot air deceleration mechanism 4 is provided inside the air inlet section 1. This mechanism reduces the hot air velocity and distributes it evenly, preventing high-speed hot air from directly carrying insufficiently dried material into the exhaust system, thereby extending the residence time of the material in the drying section 3. In this embodiment, the hot air deceleration mechanism 4 includes at least two distribution plates, arranged axially along the air inlet end 1 and coaxial with the air inlet section 1. Multiple air passages are evenly opened on the distribution plates, allowing the hot air to be evenly distributed and decelerated after passing through the distribution plates. Multiple material nozzles 5 are arranged circumferentially within the feeding section 2. Each nozzle 5 is connected to an external feeding device to atomize high-viscosity materials and spray them into the tower. Each nozzle 5 is individually controllable, allowing for independent control of its opening and closing status according to drying conditions, thus flexibly adjusting the feed rate and distribution. In this embodiment, six to eight nozzles 5 are provided. A cold air jacket 6 is fitted onto the side wall of the air inlet section 1. This jacket is connected to an external cold air device to introduce cold air into the jacket 6 to cool the side wall of the air inlet section 1, preventing the material from gelatinizing or sticking to the wall in the high-temperature zone. In this embodiment, the cold air device controls the drying process by adjusting the cold air temperature. A collection port for discharging dried material is located at the bottom of the drying section 3. In addition, there is a hot air outlet on the drying section 3. The hot air outlet is connected to the external cyclone separator. The hot air entering from the air inlet section 1 participates in the drying in the drying section and is discharged through the hot air outlet. The hot air will carry some material. After the hot air carrying the material is discharged from the hot air outlet, it will be further centrifugally separated by the subsequent cyclone separator to achieve further collection of the material.

[0021] like Figure 2 As shown, the control method includes the following steps S100-S400: S100: During the operation of the drying tower, the feed quality and discharge quality are acquired in real time, and the actual output rate is calculated based on the feed quality and discharge quality.

[0022] Specifically, in step S100, during the continuous operation of the drying tower, the mass of material entering the tower is measured in real time by a mass flow meter installed on the pipeline connecting the feeding device and the tower body as the feed mass. Simultaneously, the mass of material collected after drying is measured in real time by a quality detection device on the collection device as the discharge mass. The actual output rate is calculated as follows: Actual Output Rate = Discharge Mass / Feed Mass × 100%. This actual output rate reflects the material recovery efficiency of the drying tower under current operating conditions and is a key indicator for evaluating the drying effect.

[0023] S200: Compare the actual output rate with the target output rate range to determine whether the actual output rate deviates from the target.

[0024] Specifically, a target output rate range is pre-set according to process requirements. This range includes an upper limit and a lower limit for the target output rate. In step S200, the actual output rate calculated in step S100 is compared with this target output rate range: if the actual output rate is within the target output rate range, it indicates that the current drying effect is good and no adjustment is needed; if the actual output rate is lower than the lower limit or higher than the upper limit, it is determined that the actual output rate deviates from the target, indicating that there is an abnormality in the current drying conditions, and subsequent adjustment steps are required.

[0025] S300: When the actual output rate is lower than the lower limit of the target output rate, at least one of the hot air equipment, cold air equipment and feeding equipment shall be adjusted according to the difference between the actual output rate and the lower limit of the target output rate.

[0026] Specifically, in step S300, when the actual output rate is lower than the target output rate lower limit, it indicates that the material is not dried thoroughly or that the material entrainment loss is too large, resulting in a decrease in the effective yield. At this time, based on the difference between the actual output rate and the target output rate lower limit, at least one of the hot air equipment, cold air equipment, or feeding equipment is adjusted. For example, the output temperature of the hot air equipment can be adjusted to change the drying intensity, or the cold air flow rate of the cold air equipment can be adjusted to change the tower wall temperature to prevent material from sticking to the wall, or the feeding rate of the feeding equipment can be adjusted to change the residence time of the material in the tower. Through the coordinated or selective adjustment of the above equipment, the actual output rate is brought back towards the target output rate range.

[0027] S400: Repeat the above adjustment steps until the actual output rate stabilizes within the target output rate range.

[0028] Specifically, after performing the adjustment operation in step S300, the feed quality and discharge quality are continuously acquired in real time, and the actual output rate is calculated. The new actual output rate is then compared with the target output rate range again. If the actual output rate still does not reach the target output rate range, the adjustment operation is performed again based on the new output rate deviation value, forming a closed-loop feedback control. The above comparison and adjustment process is repeated until the actual output rate remains stable within the target output rate range, indicating that the drying tower has returned to ideal drying conditions.

[0029] Furthermore, in step S100, while acquiring the feed quality and discharge quality in real time, the wall temperature of the drying section 3 is also acquired. The wall temperature of the drying section 3 can be acquired in real time by a temperature sensor installed on the inner wall of the drying section 3. This wall temperature reflects the heat exchange state inside the drying section 3 and the thermal environment when the material comes into contact with the wall, and is an important basis for determining whether the material has become sticky and gelatinized.

[0030] In step S300, at least one of the hot air equipment, cold air equipment, and feeding equipment is adjusted based on the difference between the actual output rate and the lower limit of the target output rate, including the following steps S310-S340: S310: Compare the wall temperature with a preset safe temperature range.

[0031] Specifically, in step S310, the wall temperature is compared with a preset safe temperature range. Specifically, a safe temperature range is preset based on the material's gelatinization temperature characteristics and drying process requirements. This range includes an upper safe temperature and a lower safe temperature. The upper safe temperature is the critical temperature at which the material may gelatinize or stick to the wall, and the lower safe temperature is the minimum wall temperature required to ensure drying efficiency. By comparing the real-time collected wall temperature with this safe temperature range, it can be determined whether the current wall temperature is within a suitable range, thus providing a basis for subsequent adjustments.

[0032] S320: When the wall temperature is greater than or equal to the upper limit of the safe temperature, it is determined that the material adheres to the wall of the drying section 3; the first output rate deviation value calculated based on the actual output rate and the lower limit of the target output rate, and the first temperature deviation value calculated based on the wall temperature and the upper limit of the safe temperature are obtained.

[0033] Specifically, in step S320, when the wall temperature reaches or exceeds the upper limit of the safe temperature, it indicates that the wall temperature is too high, and there is a risk of material gelatinization or sticking to the wall. At this time, the difference between the actual output rate and the lower limit of the target output rate is calculated as the first output rate deviation value, which reflects the severity of insufficient output; simultaneously, the difference between the wall temperature and the upper limit of the safe temperature is calculated as the first temperature deviation value, which reflects the severity of wall overheating. The above two deviation values ​​together characterize the dual abnormal state of insufficient output rate and wall overheating under the current operating conditions.

[0034] S330: Determine the main control deviation type of the current working condition based on the ratio of the first output deviation value to the first temperature deviation value, and allocate the adjustment center between the hot air temperature and the cold air temperature according to the main control deviation type; Specifically, in step S330, by calculating the ratio of the first output deviation value to the first temperature deviation value, the dominance of insufficient output and wall overheating in the abnormal state can be quantified. The larger the ratio, the more prominent the insufficient output; the smaller the ratio, the more prominent the wall overheating. Based on the range of this ratio, it is determined whether the current adjustment should focus on improving the output rate or on reducing the wall temperature, thereby rationally allocating the adjustment weights between hot air temperature and cold air temperature, making the adjustment operation more targeted, and avoiding new operational imbalances caused by single adjustments.

[0035] S340: Based on the aforementioned adjustment of the center of gravity, simultaneously perform coupled adjustment to reduce the hot air temperature and reduce the cold air temperature.

[0036] Specifically, in step S340, after determining the adjustment center of the hot air temperature and the cold air temperature, the coupled operation of reducing the hot air temperature and the cold air temperature is executed simultaneously. Reducing the hot air temperature can weaken the drying intensity and reduce the heat accumulation of the material on the wall; reducing the cold air temperature can enhance the cooling effect of the cold air jacket 6 on the side wall of the air inlet section 1, directly suppressing the rise in wall temperature. The coupled adjustment of the two can effectively control the wall temperature while improving the insufficient output rate, preventing the material from gelatinizing or sticking to the wall due to overheating, and ensuring the stability of the drying process and product quality.

[0037] Furthermore, step S330 specifically includes the following steps S331-S335. It should be noted that the sequence numbers of steps S331-S335 are only for ease of explanation and do not limit the execution order of the steps. Among them, steps S332-S334 are parallel steps.

[0038] S331: Calculate the first ratio based on the proportional relationship between the first output deviation value and the first temperature deviation value.

[0039] Specifically, in step S331, the first output deviation value is denoted as ΔP, and the first temperature deviation value is denoted as ΔT. Then, the first ratio R = ΔP / ΔT. This first ratio R quantifies the relative severity of insufficient output and wall overheating in the abnormal state. The larger the R value, the more prominent the problem of insufficient output is; the smaller the R value, the more prominent the problem of wall overheating is.

[0040] S332: When the first ratio is greater than or equal to the first preset threshold, the adjustment center will be allocated to the hot air temperature adjustment.

[0041] Specifically, in step S332, when R ≥ R1 (the first preset threshold), it indicates that the insufficient output rate is the main contradiction in the current working condition, and the problem of overheating of the wall surface is relatively minor. At this time, the adjustment focus is allocated to the hot air temperature adjustment. That is, the hot air temperature is preferentially reduced to weaken the drying intensity, thereby increasing the residence time of the material in the drying section 3 and improving the thoroughness of drying, so that the output rate can be adjusted back to the target range; the cold air temperature is only used as an auxiliary adjustment and can be kept unchanged or adjusted slightly in coordination.

[0042] S333: When the first ratio is less than or equal to the second preset threshold, the adjustment focus is allocated to the cold air temperature adjustment.

[0043] Specifically, in step S333, when the first ratio is less than or equal to the second preset threshold, the adjustment focus is allocated to the cold air temperature adjustment. Specifically, when R ≤ R2 (the second preset threshold, and R2 < R1), it indicates that the overheating of the wall surface is the main contradiction in the current working condition, and the problem of insufficient output rate is relatively minor. At this time, the adjustment focus is allocated to the cold air temperature adjustment. That is, the cold air temperature is preferentially reduced to enhance the cooling effect of the cold air jacket 6 on the side wall of the air inlet section 1, directly suppressing the rise of the wall surface temperature and preventing the material from being gelatinized or sticking to the wall; the hot air temperature is only used as an auxiliary adjustment and can be kept unchanged or adjusted slightly in coordination.

[0044] S334: When the first ratio is less than the first preset threshold and greater than the second preset threshold, the adjustment step ratio of the hot air temperature and the adjustment step ratio of the cold air temperature are respectively determined by non-linear mapping according to the first ratio, where the adjustment step ratio of the hot air temperature is negatively correlated with the first ratio, and the adjustment step ratio of the cold air temperature is positively correlated with the first ratio.

[0045] Specifically, in step S334, when R2 < R < R1, it indicates that both the insufficient output rate and the overheating of the wall surface constitute significant abnormalities, and the hot air temperature and the cold air temperature need to be adjusted in coordination. Since the influence of the hot air temperature and the cold air temperature on the drying effect and the wall surface temperature shows a non-linear coupling relationship, it is difficult to balance the adjustment of the two abnormal states by using linear allocation. For this reason, in this embodiment, the adjustment step ratio α of the hot air temperature and the adjustment step ratio β of the cold air temperature are respectively determined by non-linear mapping based on the exponential function, and the calculation formula is as follows: α = exp(-k·(R - R2) / (R1 - R2)) where k is a preset sensitivity coefficient, k > 0. When the value of k is relatively large, the adjustment weight changes more steeply with the change of the R value, which is suitable for high-viscosity materials that are sensitive to the wall surface temperature; when the value of k is relatively small, the change of the adjustment weight is more gentle, which is suitable for conventional materials with relatively stable drying processes.

[0046] The design principle of this nonlinear mapping function is as follows: When R approaches R2 (i.e., the wall overheating problem is dominant), the exponent of the exponent term approaches 0, α approaches 1, and the adjustment focus shifts towards cold air temperature regulation, prioritizing the suppression of wall overheating; when R approaches R1 (i.e., the insufficient output problem is dominant), the exponent of the exponent term approaches 1, α approaches exp(-k), and the adjustment focus shifts towards hot air temperature regulation, prioritizing the improvement of drying effect; when R is at an intermediate value, α and β exhibit a continuous nonlinear transition, avoiding abrupt changes in the adjustment weights and ensuring the smoothness of the adjustment process. Through this nonlinear mapping, the proportion of hot air temperature adjustment step size α is negatively correlated with the first ratio R, and the proportion of cold air temperature adjustment step size β is positively correlated with the first ratio R, satisfying α + β = 1.

[0047] The sensitivity coefficient k can be pre-calibrated based on the thermosensitive characteristics of high-viscosity materials. For easily gelatinized materials (such as food ingredients with high sugar content or heat-sensitive drugs), a larger k value (e.g., k=2~3) is selected to quickly shift the adjustment weight to the cold air side, prioritizing the prevention of gelatinization by sticking to the wall. For materials with good thermal stability, a smaller k value (e.g., k=0.5~1) is selected to make the change in adjustment weight more gradual, balancing drying efficiency and wall temperature control. The above formula incorporates material characteristics into the adjustment strategy through a calibrable sensitivity coefficient, improving the adaptability of the control method to different materials.

[0048] S335: Determine the hot air temperature adjustment amount based on the proportion of the hot air temperature adjustment step size, and determine the cold air temperature adjustment amount based on the proportion of the cold air temperature adjustment step size.

[0049] Specifically, in step S335, after determining the proportion of hot air temperature adjustment step size α and the proportion of cold air temperature adjustment step size β, the hot air temperature adjustment amount and the cold air temperature adjustment amount are calculated respectively, based on the preset total adjustment step size or the PID calculation result based on the deviation value. For example, if the total adjustment amount is ΔU calculated based on the first output deviation value and the first temperature deviation value, then the hot air temperature adjustment amount is α·ΔU, and the cold air temperature adjustment amount is β·ΔU. Through the above allocation method, the hot air temperature and cold air temperature are coupled and adjusted according to their respective proportions, which not only maintains the consistency of the adjustment direction (simultaneously reducing the hot air temperature and cold air temperature), but also achieves a reasonable allocation of the adjustment intensity, so that the two abnormalities of insufficient output and wall overheating are synergistically improved, avoiding the operating condition oscillation caused by excessive adjustment of a single device.

[0050] Furthermore, after step S310, the following steps S350-S370 are also included: S350: When the wall temperature is lower than the preset safe lower limit, it is determined that the wall temperature absorbs heat, resulting in insufficient drying heat; a first output rate deviation value calculated based on the actual output rate and the target output rate lower limit, and a second temperature deviation value calculated based on the wall temperature and the safe lower limit.

[0051] Specifically, in step S350, when the wall temperature is lower than the preset lower limit of the safe temperature, a first output rate deviation value calculated based on the actual output rate and the target lower limit of the output rate, and a second temperature deviation value calculated based on the wall temperature and the lower limit of the safe temperature are obtained. Specifically, when the wall temperature is lower than the lower limit of the safe temperature, it indicates that the wall temperature is too low, and a large amount of heat inside the drying section 3 is absorbed by the wall, resulting in insufficient effective heat for material drying, making it difficult for the material to dry sufficiently, thus causing a decrease in output. At this time, the difference between the actual output rate and the lower limit of the target output rate is calculated as the first output rate deviation value ΔP, which reflects the severity of insufficient output; simultaneously, the difference between the lower limit of the safe temperature and the wall temperature is calculated as the second temperature deviation value ΔT', which reflects the severity of wall overcooling, i.e., the severity of heat loss. These two deviation values ​​together characterize the dual abnormal state of insufficient output and insufficient drying heat under the current operating conditions.

[0052] S360: Based on the ratio of the first output deviation value to the second temperature deviation value, determine the main control deviation type of the current working condition, and allocate the adjustment center between the hot air temperature and the cold air temperature according to the main control deviation type.

[0053] Specifically, in step S360, the main control deviation type of the current operating condition is determined based on the ratio of the first output deviation value to the second temperature deviation value, and the adjustment weight between the hot air temperature and the cold air temperature is allocated according to the main control deviation type. Specifically, by calculating the ratio R' = ΔP / ΔT' of the first output deviation value to the second temperature deviation value, the dominance of insufficient output and insufficient heat in the abnormal state can be quantified. The larger the ratio, the more prominent the insufficient output; the smaller the ratio, the more prominent the insufficient heat. Based on the range of the ratio, referring to the methods in steps S331 to S335 above, it is determined whether the current adjustment should focus on increasing the drying intensity or on compensating for heat loss from the wall, and thus the adjustment weight between the hot air temperature and the cold air temperature is reasonably allocated. When the wall temperature is too low, increasing the hot air temperature can increase the heat supply for drying, while increasing the cold air temperature can reduce the cooling effect of the cold air jacket 6 on the wall. Both help to increase the wall temperature and improve the drying effect. Therefore, the adjustment direction is opposite to that of the wall overheating condition.

[0054] S370: Based on the aforementioned adjustment of the center of gravity, simultaneously perform coupled adjustment to increase the hot air temperature and increase the cold air temperature.

[0055] Specifically, in step S370, after determining the adjustment focus of the hot air temperature and the cold air temperature, the coupled operation of increasing the hot air temperature and the cold air temperature is executed simultaneously. Increasing the hot air temperature can directly increase the heat supply for drying and improve the drying efficiency of the material; increasing the cold air temperature can reduce the cooling amount of the cold air jacket 6 on the side wall of the air inlet section 1, causing the wall temperature to rise and reducing heat loss. The coupled adjustment of the two can effectively compensate for the heat loss of the wall while improving the insufficient output rate, so that the wall temperature rises back to the safe temperature range, ensuring that there is sufficient heat supply in the drying process and preventing the output rate from remaining low due to incomplete drying.

[0056] Furthermore, after step S370, the following steps are also included: The rate of change of the wall temperature in the drying section 3 is monitored in real time. When the rate of change of the wall temperature exceeds the preset rate of change threshold, the hot air temperature adjustment amount or cold air temperature adjustment amount is reduced according to the preset ratio, and the adjustment operation is re-executed.

[0057] Specifically, during the coupled regulation process, temperature sensors installed on the inner wall of drying section 3 continuously collect the wall surface temperature and calculate the rate of change of wall surface temperature over time, i.e., the amount of temperature change per unit time. This rate of change reflects the speed and intensity of the wall surface temperature response to the regulation operation and is an important indicator for judging whether the regulation is stable. If the rate of change of wall surface temperature is too large, it indicates that the regulation operation is too drastic, which may lead to rapid fluctuations in wall surface temperature. On the one hand, this can easily cause the material to stick to the wall or gelatinize due to sudden temperature changes; on the other hand, it may also cause overshoot, making it difficult to stabilize the drying conditions through repeated oscillations.

[0058] The preset rate of change threshold is pre-calibrated based on the thermosensitive characteristics of high-viscosity materials and the thermal inertia of the drying tower. When the measured rate of change of the wall temperature exceeds this threshold, it is determined that the current adjustment operation poses an excessive risk. At this time, the hot air temperature adjustment amount or cold air temperature adjustment amount calculated in step S335 is reduced according to a preset ratio, for example, the adjustment amount is reduced to 50% of the original adjustment amount, or the reduction ratio is dynamically adjusted according to the degree of exceeding the limit of the rate of change. The reduced adjustment amount is reissued to the hot air equipment or cold air equipment for execution, so that the adjustment action tends to be gradual, avoiding drastic fluctuations in wall temperature caused by excessive adjustment in a single operation. Through the above monitoring and reduction mechanism, closed-loop safety control of the adjustment process is achieved. While ensuring that the output rate returns to the target range, the wall temperature is maintained to ensure stable changes, effectively preventing the material from gelatinizing or sticking to the wall due to sudden temperature changes, and further improving the stability of the drying process and product quality.

[0059] Furthermore, after step S310, the following steps S380-S390 are also included: S380: When the wall temperature is greater than or equal to the lower limit of the safe temperature and less than the upper limit of the safe temperature, the current working condition is determined to be insufficient in the total feed; the first output rate deviation value calculated based on the actual output rate and the lower limit of the target output rate is obtained.

[0060] Specifically, in step S380, when the wall temperature is within the safe temperature range, it indicates that the wall temperature of drying section 3 has neither reached the upper limit of the risk of gelatinization nor suffered severe heat loss due to excessively low temperatures. This means that temperature is not the primary cause of insufficient current output. At this point, the main reason for the actual output being lower than the target output lower limit can be attributed to insufficient total feed, meaning that the amount of material entering the tower per unit time fails to fully utilize the drying capacity of the hot air, resulting in the drying tower operating in an "underloaded" state. The first output deviation value ΔP (the difference between the actual output and the target output lower limit) is obtained. This deviation value directly reflects the degree of difference between the current feed amount and the ideal feed amount.

[0061] S390: Calculate the target feed increment based on the first output deviation value and increase the feeding rate of the feeding equipment.

[0062] Specifically, in step S390, based on the first output rate deviation value ΔP, combined with the current material balance relationship of the drying tower and the preset conversion coefficient, the target feed increment is calculated. For example, a mapping relationship between the output rate deviation and the feed increment can be established based on historical operating data or the material residence time model of the drying tower: Target feed increment = ΔP × K, where K is the feed compensation coefficient, which can be obtained through experimental calibration or calculated based on the rated processing capacity of the drying tower. After determining the target feed increment, the control system sends an adjustment command to the feeding equipment to increase the feeding rate of the feeding equipment, thereby increasing the feed amount per unit time. The increase in feed amount can increase the material processing load of the drying tower, making fuller use of the heat carried by the hot air, thereby increasing the actual output rate and gradually returning it to the target output rate range. At the same time, since the wall temperature is within a safe range, increasing the feed amount will not cause the risk of wall overheating, ensuring the safety of the adjustment operation.

[0063] Furthermore, in step S390, after calculating the target feed increment based on the first output deviation value and before increasing the feed rate of the feeding equipment, the following steps S380-1 to S380-3 are also included. It should be noted that the sequence numbers of steps S380-1 to S380-3 are only for ease of explanation and are not intended to limit them to being subdivided steps of step S380.

[0064] S380-1: Obtain the current open / closed status of each material nozzle 5.

[0065] Specifically, in step S380-1, since each material nozzle 5 is individually controllable, the control system records and stores the opening and closing status information of each material nozzle 5 in real time. Before increasing the feeding rate, the current status of all material nozzles 5 is first obtained to distinguish which nozzles are in the open state (feeding) and which nozzles are in the closed state (standby or not in use). Obtaining this information provides a basis for subsequent judgment on whether to prioritize opening idle nozzles or directly increase the feeding rate.

[0066] S380-2: When there are material nozzles 5 in the closed state, calculate the number of nozzles that need to be opened according to the target feed increment, and open the material nozzles 5 in the closed state in sequence according to the preset polling order.

[0067] Specifically, in step S380-2, if there are currently closed material nozzles 5, it indicates that the feeding capacity of the drying tower has not been fully released. Therefore, the feed rate is increased by opening the idle nozzles, rather than directly increasing the feeding rate of the feeding equipment. Based on the target feed increment calculated in step S390, and combined with the rated feed flow rate of a single material nozzle 5, the number of nozzles that need to be opened is calculated using the formula: Number of nozzles to be opened = Target feed increment / Rated flow rate of a single nozzle, rounded up. When opening the nozzles, they are opened sequentially according to a preset polling order. This polling order can be set based on the circumferential distribution of the nozzles (e.g., clockwise or counterclockwise rotation) or based on the historical usage time of the nozzles (prioritizing nozzles with fewer uses). Opening the nozzles in a polling order avoids uneven wear or concentrated blockage risk caused by long-term fixed use of some nozzles. It also ensures that the atomized material is more evenly distributed upwards around the 2nd circumference of the feeding section, allowing for thorough mixing with the reduced-speed hot air and improving drying uniformity.

[0068] S380-3: When all material nozzles 5 are already open, increase the feeding rate of the feeding equipment.

[0069] Specifically, in step S380-3, if all material nozzles 5 are currently open, it indicates that all nozzle resources of the drying tower have been utilized, and the feed rate cannot be increased by increasing the number of nozzles. At this point, the operation of increasing the feeding rate of the feeding equipment is executed, thereby increasing the material flow rate delivered to each nozzle per unit time to achieve an increase in the total feed rate. This tiered adjustment strategy prioritizes utilizing the adjustment margin of the number of nozzles, and adjusts the feeding rate only when the nozzle margin is exhausted. This allows for more precise feed adjustment and avoids frequent and large fluctuations in the feeding rate that could adversely affect the atomization effect and drying stability.

[0070] Furthermore, after step S380-2, the following steps S380-4 to S380-6 are also included. It should be noted that the sequence numbers of steps S380-4 to S380-6 are only for convenience of explanation and are not intended to be located after step S380-3.

[0071] S380-4: Real-time monitoring of the feeding status of newly opened material nozzle 5.

[0072] Specifically, in step S380-4, after a new material nozzle 5 is opened according to the polling sequence, the nozzle switches from the closed state to the open state and begins to inject material into the tower. Since the material nozzle 5 may fail to supply material normally due to prolonged inactivity leading to material drying or manufacturing defects, real-time monitoring of the newly opened nozzle is necessary. By using a flow sensor or pressure sensor installed on the nozzle's feed line, the feed flow rate or feed pressure is continuously collected to determine whether the nozzle has successfully opened and is supplying material stably.

[0073] S380-5: When the feed flow rate of the newly opened material nozzle 5 is lower than the preset lower flow rate limit, it is determined that the nozzle has failed to open.

[0074] Specifically, in step S380-5, if the newly opened nozzle's feed flow rate remains below a preset lower limit (which can be preset based on the rated feed flow rate and allowable fluctuation range of a single nozzle, for example, 70% of the rated flow rate) within a preset time after opening (e.g., 5 to 10 seconds), or if the feed pressure remains above a preset upper limit, then the nozzle is determined to have failed to open and cannot feed material normally. Reasons for opening failure may include internal nozzle blockage, obstructed feed lines, or nozzle valve malfunction. This determination step can promptly identify failed nozzles, preventing the actual feed rate from falling short of the expected target due to nozzles failing to feed material normally, thereby affecting the output rate adjustment effect.

[0075] S380-6: Mark the newly opened material nozzle 5 as faulty, and reselect the next material nozzle 5 that is in the closed state to be opened according to the preset polling order.

[0076] Specifically, in step S380-6, for material nozzle 5 that is determined to have failed to open, the control system marks it as faulty and removes it from the available nozzle queue. Subsequent adjustment operations will not attempt to open this nozzle until it is manually restored after manual maintenance or automatic cleaning. Simultaneously, to ensure the target feed increment is achieved, the control system selects one of the remaining closed material nozzles 5 according to a preset polling order and repeats the monitoring and judgment process from steps S380-4 to S380-5. Through the aforementioned fault marking and automatic rotation mechanism, adaptive fault-tolerant adjustment is achieved in the nozzle opening failure scenario, ensuring that even if individual nozzles fail, the feed increment target can still be achieved by activating backup nozzles, guaranteeing the continuous and stable operation of the drying tower and the effectiveness of output rate adjustment.

[0077] Furthermore, after step S390 increases the feeding rate of the feeding equipment, the following steps S390-1 to S390-3 are also included. It should be noted that the sequence numbers of steps S390-1 to S390-3 are only for convenience of explanation and are not intended to limit them to being sub-steps of step S390.

[0078] S390-1: Real-time monitoring of the feeding status of each material nozzle 5. When the feeding flow rate of any material nozzle 5 is detected to be lower than the preset lower limit, it is determined that the nozzle is blocked.

[0079] Specifically, in step S390-1, after increasing the feeding rate, the material flow rate through each material nozzle 5 per unit time increases accordingly, increasing the nozzle load and raising the risk of blockage. The feeding flow rate or feeding pressure of each nozzle is monitored in real time by flow sensors or pressure sensors installed on the feed pipes of each material nozzle 5. When the feeding flow rate of a nozzle is continuously lower than the preset lower limit (or the feeding pressure is continuously higher than the preset upper limit), the nozzle is determined to be blocked. This monitoring step can promptly detect nozzle blockage abnormalities, avoiding uneven feed distribution due to localized blockage, which in turn affects drying uniformity and yield.

[0080] S290-2: Get the number of material nozzles 5 that are currently in the closed state.

[0081] Specifically, in step SS290-2, after determining that a nozzle blockage has occurred, the control system first queries the current open / closed status of each material nozzle 5 to obtain the number of nozzles that are in the closed state (i.e., standby or not in use). This information is used to determine whether there are available standby nozzles to replace the blocked nozzles, so as to ensure that the total material supply remains unchanged and the drying conditions are stable.

[0082] S390-3: When there is a material nozzle 5 that is in a closed state, open one of the material nozzles 5 that is in a closed state according to a preset polling sequence, and close the material nozzle 5 that is blocked, so as to keep the total feed rate constant.

[0083] Specifically, in step S390-3, if there is a material nozzle 5 currently in a closed state, it indicates that there are available backup nozzle resources. At this time, one of the closed nozzles is selected to be opened according to a preset polling sequence, while the blocked nozzle is closed. Through the above "open first, close later" operation sequence, the total feed rate can be kept basically constant during the replacement process, avoiding instantaneous fluctuations in the feed rate due to a single switch. After the blocked nozzle is closed, it can be cleaned or repaired, and then added back to the polling queue after it returns to normal. Through this backup nozzle replacement mechanism, online processing of nozzle blockage faults is realized, and the normal operation of the drying tower can be restored without stopping the machine, ensuring production continuity and the stability of drying effect. At the same time, the polling sequence ensures that each nozzle has an equal opportunity to be used, avoiding some nozzles being idle for a long time while others are overused, thus extending the overall service life of the nozzles.

[0084] Furthermore, after step S200, the following steps S510-S530 are also included. It should be noted that the sequence numbers of steps S510-S530 are only for convenience of explanation and are not limited to being located after step S400. In fact, steps S510-S530 and steps S300-S400 are parallel.

[0085] S510: When the actual output rate is higher than the upper limit of the target output rate, obtain the actual humidity of the discharged material.

[0086] Specifically, in step S510, an actual output rate higher than the upper limit of the target output rate usually indicates two possibilities: first, the material drying effect is good, and the output rate is at an ideal high level; second, the material is not thoroughly dried, and the discharged material still contains high moisture content, resulting in an artificially high output quality. To distinguish between these two situations, it is necessary to obtain the actual humidity of the discharged material. The actual humidity can be collected in real time by an online moisture detector installed on the collection device. This humidity value reflects the moisture content of the dried material and is an important basis for judging whether the material is sufficiently dried.

[0087] S520: When the actual humidity is greater than or equal to the preset humidity threshold and the wall temperature is within the safe temperature range, the current abnormality is determined to be due to insufficient residence time of the material in the drying section 3; the number of material nozzles 5 currently in the open state is obtained, and the target number of nozzles to be closed is calculated based on the difference between the actual output rate and the upper limit of the target output rate.

[0088] Specifically, in step S520, a preset humidity threshold is set according to the product process requirements. When the actual humidity reaches or exceeds this threshold, it indicates that the moisture content of the discharged material is too high and the drying is incomplete. At this time, if the wall temperature is within the safe temperature range (i.e., neither too hot nor too cold), the influence of abnormal wall temperature on the drying process can be eliminated. It is determined that the main reason for the current high output rate is that the material does not stay in the drying section 3 for a long time, the feed rate is too large per unit time, and the material is discharged before it can fully contact and exchange heat with the hot air. Accordingly, the number of material nozzles 5 currently in the open state is obtained, and the target number of nozzles to be closed is calculated based on the difference between the actual output rate and the upper limit of the target output rate. The calculation formula is: target number of nozzles to be closed = (actual output rate - upper limit of target output rate) × conversion coefficient. The calculation result is rounded down and does not exceed the total number of currently open nozzles.

[0089] In S530: According to the preset polling order, the target number of material nozzles 5 that are closed are turned off, thereby reducing the number of material nozzles 5 that are still in the open state, thereby reducing the total feed amount per unit time and extending the average residence time of the material in the drying section 3.

[0090] Specifically, in step S530, after determining the target number of nozzles to be closed, the corresponding number of material nozzles 5 are closed sequentially according to a preset polling order. This polling order can be set based on the circumferential distribution of the nozzles (e.g., rotating clockwise or counterclockwise), or it can be set based on the historical usage time of the nozzles (prioritizing the closure of nozzles used more frequently) to ensure balanced wear and service life of each nozzle. After closing some nozzles, the number of remaining open material nozzles 5 decreases, the total feed rate per unit time decreases accordingly, and the average residence time of the material in the drying section 3 is extended, allowing the material to fully contact and exchange heat with the hot air, thereby improving the thoroughness of drying. Once the actual humidity of the discharged material drops below the preset humidity threshold, the actual output rate will return to the target output rate range, effectively regulating the abnormal condition of excessively high output rate.

[0091] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A control method for a low-speed drying tower, characterized in that, The low-speed drying tower includes a tower body, which includes an air inlet section (1), a feeding section (2), and a drying section (3) arranged axially. The top of the air inlet section (1) is connected to a hot air device, and the air inlet section (1) is provided with a hot air deceleration mechanism (4). Multiple material nozzles (5) are arranged circumferentially inside the feeding section (2), and the multiple material nozzles (5) are connected to an external feeding device, and each material nozzle (5) is individually controllable. The side wall of the air inlet section (1) is fitted with a cold air jacket (6), and the cold air jacket (6) is connected to a cold air device. The control method includes: During the operation of the drying tower, the feed quality and discharge quality are acquired in real time, and the actual output rate is calculated based on the feed quality and discharge quality. The actual output rate is compared with the target output rate range to determine whether the actual output rate deviates from the target. When the actual output rate is lower than the lower limit of the target output rate, at least one of the hot air equipment, cold air equipment and feeding equipment shall be adjusted according to the difference between the actual output rate and the lower limit of the target output rate. Repeat the above adjustment steps until the actual output rate stabilizes within the target output rate range.

2. The control method for a low-speed drying tower according to claim 1, characterized in that, While acquiring the feed quality and discharge quality in real time, the wall temperature of the drying section (3) is also acquired. The adjustment of at least one of the hot air equipment, cold air equipment, and feeding equipment based on the difference between the actual output rate and the lower limit of the target output rate includes: The wall temperature is compared with a preset safe temperature range; When the wall temperature is greater than or equal to the upper limit of the safe temperature, obtain a first output rate deviation value calculated based on the actual output rate and the lower limit of the target output rate, and a first temperature deviation value calculated based on the wall temperature and the upper limit of the safe temperature. Based on the ratio of the first output deviation value to the first temperature deviation value, the main control deviation type of the current working condition is determined, and the adjustment center between the hot air temperature and the cold air temperature is allocated according to the main control deviation type. Based on the aforementioned adjustment of the center of gravity, coupled adjustment of reducing hot air temperature and reducing cold air temperature is performed simultaneously.

3. The control method for a low-speed drying tower according to claim 2, characterized in that, Based on the ratio of the first output rate deviation value to the first temperature deviation value, the main control deviation type of the current operating condition is determined, and the adjustment center between the hot air temperature and the cold air temperature is allocated according to the main control deviation type, including: The first ratio is calculated based on the proportional relationship between the first output rate deviation value and the first temperature deviation value. When the first ratio is greater than or equal to the first preset threshold, the adjustment focus will be allocated to hot air temperature adjustment; When the first ratio is less than or equal to the second preset threshold, the adjustment focus will be allocated to the cold air temperature adjustment; When the first ratio is less than the first preset threshold and greater than the second preset threshold, the proportion of hot air temperature adjustment step size and the proportion of cold air temperature adjustment step size are determined by nonlinear mapping based on the first ratio, wherein the proportion of hot air temperature adjustment step size is negatively correlated with the first ratio and the proportion of cold air temperature adjustment step size is positively correlated with the first ratio. The hot air temperature adjustment amount is determined based on the proportion of the hot air temperature adjustment step size, and the cold air temperature adjustment amount is determined based on the proportion of the cold air temperature adjustment step size.

4. The control method for a low-speed drying tower according to claim 2, characterized in that, After comparing the wall temperature with a preset safe temperature range, the method further includes: When the wall temperature is lower than the preset safe lower limit, a first output rate deviation value calculated based on the actual output rate and the target output rate lower limit, and a second temperature deviation value calculated based on the wall temperature and the safe lower limit are obtained. Based on the ratio of the first output deviation value to the second temperature deviation value, the main control deviation type of the current working condition is determined, and the adjustment center between the hot air temperature and the cold air temperature is allocated according to the main control deviation type. Based on the aforementioned adjustment of the center of gravity, coupled adjustment of increasing hot air temperature and increasing cold air temperature is performed simultaneously.

5. The control method for a low-speed drying tower according to claim 2, characterized in that, After comparing the wall temperature with a preset safe temperature range, the method further includes: When the wall temperature is greater than or equal to the lower limit of the safe temperature and less than the upper limit of the safe temperature, obtain the first output rate deviation value calculated based on the actual output rate and the lower limit of the target output rate; Calculate the target feed increment based on the first output deviation value and increase the feeding rate of the feeding equipment.

6. The control method for a low-speed drying tower according to claim 5, characterized in that, Before increasing the feeding rate of the feeding equipment, the method further includes: Obtain the current opening / closing status of each material nozzle (5); When there is a material nozzle (5) in the closed state, the number of nozzles to be opened is calculated according to the target feed increment, and the material nozzles (5) in the closed state are opened in sequence according to the preset polling order. When all material nozzles (5) are in the open state, the feeding rate of the feeding equipment is increased.

7. The control method for a low-speed drying tower according to claim 2, characterized in that, After determining whether the actual output rate deviates from the target, the process also includes: When the actual output rate is higher than the upper limit of the target output rate, the actual humidity of the discharged material is obtained; When the actual humidity is greater than or equal to the preset humidity threshold and the wall temperature is within the safe temperature range, the number of material nozzles (5) currently in the open state is obtained, and the target number of nozzles to be closed is calculated based on the difference between the actual output rate and the upper limit of the target output rate. According to the preset polling order, the target number of material nozzles (5) are turned off.

8. The control method for a low-speed drying tower according to claim 3, characterized in that, After performing the coupled adjustment operation of reducing hot air temperature and reducing cold air temperature simultaneously based on the adjusted center of gravity, the method further includes: Real-time monitoring of the rate of change of wall temperature in the drying section (3); When the rate of change of the wall temperature exceeds the preset rate of change threshold, the hot air temperature adjustment amount or cold air temperature adjustment amount is reduced according to the preset ratio, and the adjustment operation is re-executed.

9. The control method for a low-speed drying tower according to claim 6, characterized in that, After increasing the feeding rate of the feeding equipment, the method further includes: The feeding status of each material nozzle (5) is monitored in real time. When the feeding flow rate of any material nozzle (5) is lower than the preset lower limit of flow rate, it is determined that the nozzle is blocked. Get the number of material nozzles (5) that are currently closed; When there is a material nozzle (5) in the closed state, open a material nozzle (5) in the closed state according to the preset polling order, and close the material nozzle (5) that is blocked.

10. The control method for a low-speed drying tower according to claim 6, characterized in that, After sequentially opening the material nozzles (5) that are in the closed state according to a preset polling order, the method further includes: Real-time monitoring of the feeding status of newly opened material nozzles (5); When the feed flow rate of the newly opened material nozzle (5) is lower than the preset lower limit of flow rate, the newly opened material nozzle (5) is marked as faulty, and the next material nozzle (5) in the closed state is re-selected and opened according to the preset polling order.

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