Counterflow integrated asphalt station hot blast stove and temperature self-adaptive control method thereof

Abstract

The application provides a counterflow integrated asphalt station hot blast furnace and a temperature self-adaptive control method thereof. The hearth of the hot blast furnace is sequentially provided with a furnace shell, a heat insulation layer and a refractory working layer from outside to inside. The refractory working layer is fixed by an anchoring member and is provided with expansion joints in sections. The inner cavity of the hearth adopts a convolute configuration. The hot blast outlet is provided with a flow guiding and equalizing structure. The temperature control adopts a PID control based on fuzzy rule online adjustment parameters, and is combined with a working condition feedforward and an over-temperature protection interlock with a built-in large lag compensation link. The application can effectively relieve the high-temperature deformation of the furnace body, improve the temperature control stability, reduce the operation and maintenance cost and guarantee the production quality of finished products.

Description

Technical Field

[0001] This invention relates to the technical field of asphalt mixture mixing equipment, specifically to a counter-current integrated asphalt station hot air furnace and its temperature adaptive control method. Background Technology

[0002] Counter-current integrated asphalt mixing plants are widely used in asphalt mixture production. The hot blast stove, as the core heating component, typically consists of a burner, a hot blast furnace, and a counter-current drying drum. The burner generates high-temperature hot air within the furnace, which is then sent into the counter-current drying drum for heat exchange with the aggregate. This provides advantages such as high heat exchange efficiency and high discharge temperature, making it suitable for production requiring a large proportion of recycled materials. However, under long-term high-temperature operation, the existing hot blast stove's steel shell directly bears the high-temperature radiation and thermal shock of the internal flames, making it prone to high-temperature oxidation, creep deformation, and even burn-through. This results in a short furnace lifespan and frequent routine maintenance. Furthermore, the existing hot blast stove's internal lining structure is poorly designed, with insufficient insulation between the refractory working layer and the furnace shell, leading to an overall high furnace shell temperature. The lining anchoring structure is also unreliable, lacking a proper expansion joint structure. Under long-term thermal expansion and contraction cycles, the lining is prone to cracking and detachment, further exacerbating localized overheating and deformation of the furnace shell.

[0003] In terms of temperature control, the combustion heat exchange link between the hot blast furnace and the counter-current drying drum exhibits significant lag and inertia. Furthermore, the actual heat load of the furnace fluctuates drastically with changes in aggregate feed rate, aggregate moisture content, and ambient temperature. Traditional hot blast furnaces often employ fixed-parameter PID control, which struggles to adapt to complex and changing operating conditions, generally exhibiting slow temperature response, large control overshoot, and significant furnace temperature fluctuations. This leads to fuel waste and increased production costs. Additionally, the furnace body is subjected to repeated, drastic temperature changes and thermal shocks, accelerating structural aging and deformation. Furthermore, the unstable hot blast outlet temperature directly affects the discharge temperature of the dried aggregate, hindering the stable quality control of the finished asphalt mixture. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a counter-current integrated hot air furnace for asphalt plants and its temperature adaptive control method, which effectively alleviates high-temperature deformation of the furnace body, improves temperature control stability, reduces operating and maintenance costs, and ensures the quality of finished product production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A counter-current integrated hot blast stove for asphalt plants includes a hot blast furnace, a burner, a counter-current drying drum, and a temperature adaptive control system. The burner is fixedly installed inside the combustion chamber of the hot blast furnace. The high-temperature flue gas generated by the combustion of fuel in the burner is fully combusted in the hot blast furnace to form high-temperature hot air. The hot air outlet of the hot blast furnace is connected to the air inlet of the counter-current drying drum. The high-temperature hot air is sent into the counter-current drying drum and exchanges heat with the aggregate moving in the opposite direction. The temperature adaptive control system includes a temperature detection unit, an actuator, and a controller. The temperature detection unit is respectively located inside the hot blast furnace and at the hot air outlet. The temperature detection unit is used to collect the furnace temperature and the hot air outlet temperature in real time. The actuator includes… The fuel supply regulating device and combustion air fan are both connected to the burner. The actuator is used to regulate the fuel supply and combustion air volume of the burner to match the air-fuel ratio. The controller is electrically connected to the temperature detection unit and the actuator. The hot blast furnace is arranged from the outside to the inside as a furnace shell, a heat insulation layer, and a refractory working layer. The refractory working layer is fixedly connected to the inner wall surface of the furnace shell by anchors. The refractory working layer is provided with expansion joints in sections along the extension direction of the furnace. The inner cavity of the hot blast furnace adopts a swirling configuration. A flow guiding and equalizing structure is set at the hot air outlet of the hot blast furnace. The controller adopts a PID controller with online parameter adjustment based on fuzzy rules. The controller has a built-in large hysteresis compensation element.

[0007] Preferably, the heat insulation layer is installed close to the inner wall of the furnace shell, and the heat insulation layer is made of aluminum silicate ceramic fiber material; the refractory working layer is located on the innermost side of the furnace chamber, and the refractory working layer is integrally cast with high alumina refractory castable or constructed by building with mullite refractory bricks.

[0008] Preferably, the anchor is a Y-shaped anchor or a hexagonal mesh, with one end fixed to the inner wall of the furnace shell and the other end embedded in the refractory working layer. The expansion joint is evenly segmented along the length of the refractory working layer.

[0009] Preferably, a reinforcing ring and reinforcing ribs are provided on the outer surface of the furnace shell, and a cooling circulating air interlayer is provided between the furnace shell and the heat insulation layer, the cooling circulating air interlayer being connected to an external cooling air duct.

[0010] Preferably, the temperature detection unit further includes a temperature detection element disposed on the outer surface of the furnace shell, the temperature detection element being used to collect the surface temperature of the furnace shell in real time.

[0011] A temperature adaptive control method for a counter-current integrated asphalt plant hot air furnace includes: taking a set target temperature as the control target, collecting the current furnace temperature and hot air outlet temperature in real time through a temperature detection unit, calculating the temperature deviation and the rate of change of temperature deviation, fuzzifying the temperature deviation and the rate of change of temperature deviation, adjusting the proportional coefficient, integral coefficient and derivative coefficient of the PID controller online according to a preset fuzzy rule table, compensating for the hysteresis characteristics of the combustion heat exchange link by combining a large hysteresis compensation link, and outputting the control quantity to the actuator to adjust the fuel supply and combustion air volume of the burner.

[0012] Preferably, fuzzy rule reasoning is performed based on a preset 7×7 fuzzy rule table, and after online parameter adjustment, defuzzification is performed to output the final PID control parameters.

[0013] Preferably, the large hysteresis compensation stage employs a Smith predictor, which compensates for the pure hysteresis characteristics of the combustion heat exchange stage through a prediction model.

[0014] Preferably, feedforward correction is performed by combining the operating conditions information such as aggregate feed rate, aggregate moisture content, and ambient temperature to adjust the target temperature value or controller parameters. When the furnace temperature or furnace shell surface temperature exceeds the set threshold, an alarm signal is issued and the burner load is automatically reduced until the fuel supply is cut off.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The furnace chamber adopts a multi-layer composite structure consisting of a furnace shell, a heat insulation layer, and a refractory working layer. The heat insulation layer effectively blocks the heat inside the furnace chamber from being conducted to the furnace shell, reducing the working temperature of the furnace shell and preventing it from deforming or burning due to long-term high-temperature operation. This extends the overall service life of the furnace body and reduces equipment maintenance costs.

[0017] The refractory working layer is fixedly connected to the inner wall of the furnace shell with anchors, which improves the adhesion stability of the lining structure and avoids the lining from falling off or collapsing during long-term operation. The refractory working layer is equipped with expansion joints in sections, which can absorb the expansion deformation of the refractory material caused by heat, prevent the lining from cracking due to thermal expansion stress, and at the same time prevent the thermal expansion from directly compressing the furnace shell and causing deformation.

[0018] The furnace interior adopts a swirling configuration, which guides the flame and air distribution to form a vortex inside the furnace, extending the flow path of high-temperature flue gas, promoting thorough mixing of flue gas and heat, preventing the flame from directly impacting local furnace walls and forming hot spots, and balancing the heating state of the furnace walls. The hot air outlet is equipped with a flow guiding and equalizing structure to ensure a uniform temperature field distribution of the hot air entering the counter-current drying drum, improving the consistency of aggregate heat transfer.

[0019] The system employs a PID control method based on fuzzy rules for online parameter adjustment. The controller parameters can be automatically adjusted according to operating conditions, adapting to the furnace's high inertia and time-varying operating characteristics. Combined with a large hysteresis compensation circuit, it can compensate for the hysteresis characteristics of the combustion heat exchange process, reducing temperature control overshoot, accelerating the response speed to changes in operating conditions, reducing fuel consumption, and mitigating the repeated thermal shocks experienced by the furnace body.

[0020] By incorporating operating condition information such as aggregate feed rate, aggregate moisture content, and ambient temperature, feedforward corrections are made to improve the adaptability of the control method to different operating conditions. An over-temperature protection interlock logic is set up to automatically adjust the burner load or even cut off fuel when the temperature exceeds the limit, preventing overheating damage to the furnace body and ensuring safe equipment operation.

[0021] After the furnace temperature control stability is improved, the hot air outlet temperature remains stable, thereby ensuring that the aggregate discharge temperature is stable and controllable, which is conducive to improving the production quality of finished asphalt mixtures and meeting high-standard production requirements. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the hot air furnace in this invention;

[0024] Figure 3 This is a block diagram of a temperature adaptive control system.

[0025] Figure 4 This is a flowchart of the method of the present invention.

[0026] in:

[0027] 1. Burner; 2. Hot air furnace; 21. Furnace shell; 22. Insulation layer; 23. Refractory working layer; 24. Anchor; 25. Expansion joint; 3. Feed box; 4. Countercurrent drying drum; 5. Temperature detection unit. Detailed Implementation

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] like Figure 1 , Figure 2 As shown, a counter-current integrated asphalt plant hot air furnace is applied to a counter-current integrated asphalt mixing plant to generate high-temperature hot air and send it into the drying drum to complete the drying and heating of aggregates.

[0030] Overall composition:

[0031] This hot blast furnace 2 mainly includes a hot blast furnace chamber 2, a burner 1, a counter-current drying drum 4, and a temperature adaptive control system. The burner 1 is installed inside the combustion chamber of the hot blast furnace 2. Fuel is injected through the burner 1 and burned inside the hot blast furnace 2. The resulting high-temperature flue gas is fully combusted inside the hot blast furnace 2 to form high-temperature hot air. The hot air outlet of the hot blast furnace 2 is connected to the air inlet of the counter-current drying drum 4. After the high-temperature hot air is sent into the counter-current drying drum 4, it forms a counter-current heat exchange with the aggregate moving in the opposite direction inside the drum, completing the drying and heating of the aggregate. The flue gas after heat exchange is discharged from the other end of the drying drum.

[0032] Furthermore, a material drop box 3 is installed between the hot air outlet of the hot air furnace 2 and the air inlet of the counter-current drying drum 4 for conveying raw materials.

[0033] Internal deformation-resistant structure of the furnace:

[0034] The second chamber of the hot blast stove adopts a multi-layered composite structure, consisting of a furnace shell 21, an insulation layer 22, and a refractory working layer 23 arranged sequentially from the outside in. The furnace shell 21 is a cylindrical structure welded from steel plates, forming the main outer wall of the second chamber of the hot blast stove. The insulation layer 22 is installed close to the inner wall of the furnace shell 21 and is made of lightweight aluminosilicate ceramic fiber insulation material to prevent heat from the inside of the furnace from being conducted to the furnace shell 21, thereby reducing the operating temperature of the furnace shell 21. The refractory working layer 23 is located on the innermost side of the furnace chamber and is integrally cast using high-alumina refractory castable or constructed using mullite refractory bricks, directly bearing the scouring effect of the flames and high-temperature flue gas inside the furnace chamber.

[0035] The refractory working layer 23 is fixedly connected to the inner wall of the furnace shell 21 by anchors 24. The anchors 24 are Y-shaped anchors or hexagonal wire mesh. One end of the anchor 24 is fixedly connected to the inner wall surface of the furnace shell 21, and the other end is embedded in the interior of the refractory working layer 23 to prevent the refractory working layer 23 from falling off or collapsing during long-term operation. Expansion joints 25 are provided in sections along the extension direction of the furnace chamber in the refractory working layer 23. The expansion joints 25 are used to absorb the deformation caused by the thermal expansion of the refractory material, so as to avoid cracking of the refractory working layer 23 due to thermal expansion stress, or deformation of the furnace shell 21 caused by thermal expansion pressing on it.

[0036] The inner cavity of the second chamber of the hot blast furnace adopts a swirling configuration. The flame injected by the burner 1 and the secondary air distribution form a swirling flow inside the furnace, extending the flow path of the high-temperature flue gas and ensuring thorough mixing of the flue gas and heat. This prevents the flame from directly impacting local furnace walls and forming local hot spots. A flow guiding and equalizing structure is installed at the hot air outlet of the second chamber of the hot blast furnace to ensure a uniform temperature distribution of the hot air entering the counter-current drying drum 4, thereby improving heat exchange consistency.

[0037] The outer surface of the furnace shell 21 is provided with reinforcing rings and ribs to improve the overall structural rigidity of the shell and, together with the internal insulation structure, reduce the deformation of the furnace body caused by thermal stress. A cooling circulating air jacket is provided between the furnace shell 21 and the insulation layer 22. The cooling circulating air jacket is connected to the external cooling air duct, and the circulating air is used to force-cool the furnace shell 21, further reducing the operating temperature of the furnace shell 21.

[0038] Temperature adaptive control system such as Figure 3 As shown:

[0039] The temperature adaptive control system mainly includes a temperature detection unit 5, an actuator, and a controller.

[0040] The temperature detection unit 5 includes a temperature detection element installed inside the hot air furnace 2, a temperature detection element installed at the hot air outlet, and a temperature detection element installed on the outer surface of the furnace shell 21. Each temperature detection element uses a thermocouple to collect the furnace temperature, the hot air outlet temperature, and the surface temperature of the furnace shell 21 in real time.

[0041] The actuator includes a fuel supply regulating device and a combustion air blower. Both the fuel supply regulating device and the combustion air blower are connected to the burner 1 and are used to regulate the fuel supply and combustion air volume of the burner 1, respectively, to achieve a coordinated matching of the air-fuel ratio.

[0042] The controller employs a PID controller with adaptive parameter adjustment based on fuzzy rules. It incorporates a large lag compensation element, which utilizes a Smith predictor. The controller is electrically connected to both the temperature detection unit 5 and the actuator, receiving temperature detection signals and outputting control commands to the actuator.

[0043] Temperature adaptive control process:

[0044] like Figure 4 As shown, the temperature adaptive control in this embodiment is performed according to the following steps:

[0045] The first step is to use the preset target temperature as the control target, and collect the current furnace temperature and hot air outlet temperature in real time through the temperature detection unit 5, and calculate the temperature deviation and the rate of change of temperature deviation.

[0046] The second step is to fuzzify the temperature deviation and the rate of change of temperature deviation, and perform fuzzy rule reasoning based on the preset 7×7 fuzzy rule table. The proportional coefficient, integral coefficient and derivative coefficient of the PID controller are adjusted online so that the controller parameters change automatically with the operating conditions to adapt to the large inertia and time-varying characteristics of the furnace.

[0047] The third step involves defuzzification after parameter adjustment, outputting the final control parameters. To address the significant time lag in the combustion and heat exchange processes, the Smith predictor model is used to compensate for the pure time lag, reducing control overshoot and accelerating system response.

[0048] The fourth step involves combining the operating conditions information such as aggregate feed rate, aggregate moisture content, and ambient temperature to perform feedforward correction, and adjusting the target temperature value or controller parameters accordingly to achieve adaptive adaptation to changes in operating conditions.

[0049] The fifth step is to set the over-temperature protection interlock logic. When the detected furnace temperature or the surface temperature of the furnace shell 21 exceeds the set safety threshold, the controller will issue an alarm signal and automatically reduce the operating load of the burner 1 until the fuel supply is cut off to prevent the furnace body from overheating and being damaged.

Claims

1. A counter-current integrated hot air furnace for asphalt plants, characterized in that, The system includes a hot blast furnace, a burner, a counter-current drying drum, and a temperature adaptive control system. The burner is fixedly installed inside the combustion chamber of the hot blast furnace. The high-temperature flue gas generated by the combustion of fuel in the burner is fully combusted in the furnace to form high-temperature hot air. The hot air outlet of the furnace is connected to the air inlet of the counter-current drying drum. The high-temperature hot air is sent into the drum and exchanges heat with the aggregate moving in the opposite direction. The temperature adaptive control system includes a temperature detection unit, an actuator, and a controller. The temperature detection units are located inside the furnace and at the hot air outlet. These units are used to collect the furnace temperature and the hot air outlet temperature in real time. The actuator includes a fuel supply regulating device. The combustion air blower is located within the burner; the fuel supply regulating device and the combustion air blower are both connected to the burner; the actuator is used to regulate the fuel supply and combustion air volume of the burner to match the air-fuel ratio; the controller is electrically connected to the temperature detection unit and the actuator respectively; the hot air furnace is arranged from the outside to the inside as a furnace shell, a heat insulation layer, and a refractory working layer; the refractory working layer is fixedly connected to the inner wall surface of the furnace shell by anchors; the refractory working layer is provided with expansion joints in sections along the extension direction of the furnace; the inner cavity of the hot air furnace adopts a swirling configuration; a flow guiding and equalizing structure is set at the hot air outlet position of the hot air furnace; the controller adopts a PID controller based on fuzzy rules for online parameter adjustment, and the controller has a built-in large hysteresis compensation element.

2. The counter-current integrated hot air furnace for asphalt plants as described in claim 1, characterized in that, The heat insulation layer is installed close to the inner wall of the furnace shell and is made of aluminum silicate ceramic fiber material; the refractory working layer is located at the innermost side of the furnace chamber and is integrally cast with high alumina refractory castable or constructed by building with mullite refractory bricks.

3. The counter-current integrated hot air furnace for asphalt plants as described in claim 1, characterized in that, The anchors are Y-shaped anchors or hexagonal mesh. One end of the anchor is fixed to the inner wall of the furnace shell, and the other end is embedded in the interior of the refractory working layer. The expansion joints are evenly segmented along the length of the refractory working layer.

4. The counter-current integrated hot blast stove for asphalt plants as described in claim 1, characterized in that, The outer surface of the furnace shell is provided with reinforcing rings and reinforcing ribs, and a cooling circulating air interlayer is provided between the furnace shell and the heat insulation layer. The cooling circulating air interlayer is connected to the external cooling air duct.

5. A counter-current integrated hot air furnace for asphalt plants as described in claim 1, characterized in that, The temperature detection unit also includes a temperature detection element disposed on the outer surface of the furnace shell, which is used to collect the surface temperature of the furnace shell in real time.

6. A temperature adaptive control method for a hot blast stove in a counter-current integrated asphalt plant as described in any one of claims 1 to 5, characterized in that, include: With the set target temperature as the control target, the current furnace temperature and hot air outlet temperature are collected in real time through the temperature detection unit. The temperature deviation and the rate of change of temperature deviation are calculated. The temperature deviation and the rate of change of temperature deviation are fuzzified. According to the preset fuzzy rule table, the proportional coefficient, integral coefficient and derivative coefficient of the PID controller are adjusted online. Combined with the large hysteresis compensation link, the hysteresis characteristics of the combustion heat exchange link are compensated. The control quantity is output to the actuator to adjust the fuel supply and combustion air volume of the burner.

7. A counter-current integrated hot blast stove for asphalt plants as described in claim 6, characterized in that, Based on the preset 7×7 fuzzy rule table, fuzzy rule reasoning is performed. After online parameter adjustment, defuzzification is performed, and the final PID control parameters are output.

8. A counter-current integrated hot blast stove for asphalt plants as described in claim 6, characterized in that, The large lag compensation stage uses the Smith predictor to compensate for the pure lag characteristics of the combustion heat exchange stage through a prediction model.

9. A counter-current integrated hot blast stove for asphalt plants as described in claim 6, characterized in that, By combining the operating conditions information such as aggregate feed rate, aggregate moisture content, and ambient temperature, feedforward correction is performed to adjust the target temperature value or controller parameters. When the furnace temperature or furnace shell surface temperature exceeds the set threshold, an alarm signal is issued and the burner load is automatically reduced until the fuel supply is cut off.

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