A gas-fired boiler flue gas waste heat recovery and utilization system

Abstract

The present application relates to gas boiler energy saving technical field, especially a kind of gas boiler flue gas waste heat recovery and utilization system, including exhaust flue, pulsating heat pipe heat exchange component, flue gas parameter sensing module, cold source medium supply module, exhaust flue temperature sensor, outlet temperature sensor and control module.Control module includes adjustment scheme generation module, optimization module and scheme constraint unit;Adjustment scheme generation module generates basic adjustment scheme according to flue gas temperature, flow parameter;Optimization module carries out first optimization and second optimization to basic scheme according to exhaust flue temperature deviation and cold source medium outlet temperature deviation, obtains final target scheme;Variable frequency circulating pump operates according to final target scheme.The present application realizes that cold source medium flow and flue gas real-time heat load dynamically match, solves the problem that cold source medium flow cannot be self-adaptively regulated, and waste heat recovery is insufficient.

Description

Technical Field

[0001] This invention relates to the field of energy-saving technology for gas-fired boilers, and in particular to a waste heat recovery and utilization system for flue gas from gas-fired boilers. Background Technology

[0002] Existing flue gas waste heat recovery technologies for gas-fired boilers mostly employ pulsed heat pipe heat exchangers or a combination of high-temperature oil heat exchangers and oil storage tanks to recover waste heat from flue gas. In pulsed heat pipe heat exchangers, the cold source medium passively flows in due to pipeline pressure, while in high-temperature oil heat exchangers and oil storage tanks, oil circulation is spontaneously driven by density differences. Neither of these existing technologies establishes an active flow regulation mechanism on the cold source medium side that is correlated with the real-time heat load of the flue gas. This results in the inability to dynamically match the cold source medium flow rate according to the waste heat status of the flue gas, leading to insufficient waste heat recovery.

[0003] Chinese Patent Publication (Announcement) No. CN118031201A discloses a waste heat recovery system for flue gas and a waste heat boiler system. However, it still suffers from the problem of the cold source medium passively flowing in due to the pipeline pressure and the lack of an active flow regulation mechanism associated with the real-time heat load of the flue gas. This results in the cold source medium flow rate being unable to be dynamically matched according to the waste heat status of the flue gas, leading to insufficient waste heat recovery from the flue gas.

[0004] Chinese Patent Publication (Announcement) No. CN115111566A discloses a waste heat recovery boiler and a waste heat recovery method, but it still has the problem of oil circulation relying on density difference for spontaneous drive and not establishing an active flow regulation mechanism related to the real-time heat load of flue gas. This results in the cold source medium flow rate not being able to be dynamically matched according to the waste heat status of the flue gas, and insufficient waste heat recovery of flue gas. Summary of the Invention

[0005] To address this issue, the present invention provides a waste heat recovery system for gas-fired boiler flue gas, which overcomes the problem that the flow rate of the cold source medium in existing gas-fired boiler flue gas waste heat recovery systems cannot be adjusted according to the real-time heat load of the flue gas, resulting in insufficient waste heat recovery.

[0006] To achieve the above objectives, the present invention provides a waste heat recovery and utilization system for flue gas from a gas-fired boiler, comprising: The flue gas parameter sensing module includes a temperature sensor and a flow sensor. The temperature sensor and flow sensor are located inside the flue gas duct and upstream of the heat exchange component. A flue gas temperature sensor is located downstream of the heat exchange component. A cold source medium supply module, which is connected to a heat exchange component, includes an inlet pipe and a variable frequency circulating pump. An inlet temperature sensor is provided on the inlet pipe, and the variable frequency circulating pump is located on the inlet pipe. One end of the inlet pipe is connected to the cold source medium supply module, and the other end is connected to the heat exchange component. A heat exchange component is provided with an outlet pipe, an outlet temperature sensor is provided on the outlet pipe, and the outlet pipe is connected to a heat energy utilization device; The system collects flue gas data through a flue gas parameter sensing module, a cold source medium supply module, a flue gas temperature sensor, an inlet temperature sensor, and an outlet temperature sensor. The control module is electrically connected to the flue gas parameter sensing module, the outlet temperature sensor, the exhaust gas temperature sensor, the variable frequency circulating pump, and the inlet temperature sensor. The control module includes: The adjustment scheme generation module is used to generate an adjustment scheme for the basic cold source medium based on flue gas data; The optimization module is used to perform a first optimization on the basic cold source medium adjustment scheme, and then perform a second optimization on the first optimization process to obtain the second optimized adjustment scheme. The second optimized adjustment scheme is then output as the final target scheme. The variable frequency circulating pump operates at the speed according to the final target scheme.

[0007] Furthermore, the flue gas parameters include flue gas temperature parameters, flue gas flow rate parameters, basic inlet temperature parameters of the cold source medium, actual outlet temperature parameters of the cold source medium, and actual exhaust gas temperature parameters. The temperature sensor is used to collect flue gas temperature parameters, the flow sensor is used to collect flue gas flow parameters, and the exhaust gas temperature sensor is used to collect actual exhaust gas temperature parameters. The inlet temperature sensor is used to collect the basic inlet temperature parameters of the cold source medium, and the outlet temperature sensor is used to collect the actual outlet temperature parameters of the cold source medium. The adjustment scheme generation module calculates the basic flow rate value based on the flue gas temperature parameter, flue gas flow rate parameter, target exhaust gas temperature parameter, basic inlet temperature parameter of the cold source medium, and target outlet temperature parameter, and outputs the basic flow rate value as the basic cold source medium adjustment scheme.

[0008] Furthermore, the heat exchange component is a pulsating heat pipe heat exchange component, which includes a cold source chamber, a heat source chamber, and pulsating heat pipes. The heat source chamber is connected to the flue gas duct. Part of the pulsating heat pipe is installed in the cold source chamber, and another part is installed in the heat source chamber. The cold source chamber has a cold source medium inlet and a cold source medium outlet. The cold source medium inlet is connected to the inlet pipe, and the cold source medium outlet is connected to the outlet pipe.

[0009] Furthermore, the optimization module includes a first optimization unit and a second optimization unit. The first optimization unit is used to perform a first optimization on the basic cold source medium adjustment scheme to obtain a first-optimized adjustment scheme. The second optimization unit is used to perform a second optimization on the first optimization process to obtain a second-optimized adjustment scheme.

[0010] Furthermore, the first optimization unit performs a first-order optimization on the basic cold source medium adjustment scheme to obtain a post-optimized adjustment scheme, including: The exhaust temperature deviation is calculated based on the actual and target exhaust temperature parameters, and then compared with a preset exhaust temperature deviation threshold. When the flue gas temperature deviation is greater than the preset flue gas deviation threshold, the basic cold source medium regulation scheme is optimized once. The optimization includes: performing incremental compensation calculation on the basic flow value according to the flue gas temperature deviation to obtain the optimized flow value, and replacing the basic flow value in the basic cold source medium regulation scheme with the optimized flow value to obtain the optimized regulation scheme. When the flue gas temperature deviation is less than or equal to the preset flue gas deviation threshold, the basic cold source medium adjustment scheme will not be optimized once, and the basic cold source medium adjustment scheme will be output as the optimized adjustment scheme.

[0011] Furthermore, the second optimization unit performs a second optimization on the first optimization process to obtain a second-optimized adjustment scheme, including: The outlet water temperature deviation is calculated based on the actual outlet temperature parameters of the cold source medium and the target outlet temperature parameters. The outlet water temperature deviation is then compared with a preset outlet water deviation threshold, where: When the outlet water temperature deviation is greater than the preset outlet water deviation threshold, the first optimization process is optimized again. The second optimization includes: performing a correction and compensation calculation on the flow rate value after the first optimization based on the outlet water temperature deviation to obtain the flow rate value after the second optimization, and replacing the flow rate value after the first optimization in the adjustment scheme after the first optimization with the flow rate value after the second optimization to obtain the adjustment scheme after the second optimization. When the outlet water temperature deviation is less than or equal to the preset outlet water deviation threshold, the first optimization process will not be optimized a second time, and the adjustment scheme after the first optimization will be output as the adjustment scheme after the second optimization.

[0012] Furthermore, the control module also includes a scheme constraint module, which is used to impose flow constraints on the secondary optimization adjustment scheme to obtain a constrained adjustment scheme, and replace the content of the secondary optimization adjustment scheme with the content of the constrained adjustment scheme.

[0013] Furthermore, the scheme constraint module includes a lower limit constraint unit and an upper limit constraint unit. The secondary optimization adjustment scheme includes a secondary optimization flow value. The lower limit constraint unit is used to set the constraint flow value according to the secondary optimization flow value in the secondary optimization adjustment scheme. The upper limit constraint unit is used to perform flow constraint on the secondary optimization adjustment scheme according to the constraint flow value to obtain the constrained adjustment scheme, and replace the content of the secondary optimization adjustment scheme with the content of the constrained adjustment scheme.

[0014] Furthermore, the lower limit constraint unit sets the constraint flow value based on the secondary optimized flow value in the secondary optimized adjustment scheme, including: The optimized flow rate value is compared with the preset minimum flow rate, where: When the flow rate after secondary optimization is less than the preset minimum flow rate, the preset minimum flow rate will be output as the constraint flow rate value. When the optimized flow rate is greater than or equal to the preset minimum flow rate, the optimized flow rate will be output as the constraint flow rate.

[0015] Further, the upper limit constraint unit applies flow constraints to the secondary optimized adjustment scheme based on the constraint flow value to obtain the constrained adjustment scheme, and replaces the content of the secondary optimized adjustment scheme with the content of the constrained adjustment scheme, including: The constrained flow rate value is compared with the preset maximum flow rate, where: When the constrained flow rate is greater than the preset maximum flow rate, the preset maximum flow rate is output as the final flow rate value, and the second-optimized flow rate value in the second-optimized adjustment scheme is replaced with the final flow rate value to obtain the constrained adjustment scheme. The content of the second-optimized adjustment scheme is then replaced with the content of the constrained adjustment scheme. When the constraint flow value is less than or equal to the preset maximum flow, the constraint flow value is output as the final flow value, and the secondary optimized flow value in the secondary optimized adjustment scheme is replaced with the final flow value to obtain the constraint adjustment scheme. The content of the secondary optimized adjustment scheme is then replaced with the content of the constraint adjustment scheme.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The waste heat recovery system for gas-fired boilers provided by this invention, based on the collection of flue gas data through a flue gas parameter sensing module, a cold source medium supply module, an exhaust gas temperature sensor, and an outlet temperature sensor, and the generation of a basic cold source medium regulation scheme according to the regulation scheme generation module, adds an optimization module. The first optimization unit of the optimization module performs a primary optimization of the basic cold source medium regulation scheme, addressing the lack of temperature feedback based on the actual exhaust gas temperature deviation, thereby improving the control accuracy of the cold source medium flow rate. The second optimization unit performs a secondary optimization of the primary optimization process, resolving the issue of only considering the exhaust gas temperature deviation without considering the actual outlet temperature deviation of the cold source medium. The system addresses the mismatch issue on the cold source side by enabling fine-tuning of the cold source medium side, thereby achieving dynamic matching between the cold source medium flow rate and the real-time heat load of the flue gas, thus improving the efficiency of flue gas waste heat recovery. Furthermore, the system uses a scheme constraint module to constrain the flow rate of the secondary optimized adjustment scheme, resolving the risk of equipment damage caused by the flow rate exceeding the safe operating boundary after secondary optimization in existing technologies, achieving safe operation under dual-layer boundary protection. Finally, by using a variable frequency circulating pump operating at the speed according to the final target scheme, the system solves the problem of insufficient flue gas waste heat recovery caused by the disconnect between the cold source medium flow rate and the flue gas waste heat state in existing technologies, thereby improving the efficiency of flue gas waste heat recovery. Attached Figure Description

[0017] Figure 1 A simplified structural diagram of a waste heat recovery and utilization system for flue gas from a gas-fired boiler. Figure 2 Here is a simplified structural diagram of the heat exchange assembly; Figure 3 This is a schematic diagram of the control module in Example 1; Figure 4 This is a logic diagram of the first optimization unit in Example 1; Figure 5 This is a schematic diagram of the control module in Example 2; Figure 6 This is a logic diagram of the lower limit constraint unit in Example 2. Detailed Implementation

[0018] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0021] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] Example 1: Please see Figure 1 The diagram shown is a simplified structural diagram of the waste heat recovery and utilization system for gas-fired boiler flue gas in this embodiment. The system includes: The flue gas parameter sensing module includes a temperature sensor 3 and a flow sensor 4. The temperature sensor 3 and the flow sensor 4 are located in the flue gas duct 2 and upstream of the heat exchange component 5. A flue gas temperature sensor 14 is located downstream of the heat exchange component 5. The flue duct 2 is connected to the boiler 1; The cold source medium supply module is connected to the heat exchange component 5 and includes an inlet pipe 7 and a variable frequency circulating pump 8. An inlet temperature sensor 9 is provided on the inlet pipe 7. The variable frequency circulating pump 8 is located on the inlet pipe 7. One end of the inlet pipe 7 is connected to the cold source medium supply module 6 and the other end is connected to the heat exchange component 5. The heat exchange assembly 5 is provided with an outlet pipe 10, an outlet temperature sensor 11 is provided on the outlet pipe 10, and the outlet pipe 10 is connected to the heat energy utilization device 12. The system collects flue gas data through a flue gas parameter sensing module, a cold source medium supply module, a flue gas temperature sensor 14, an inlet temperature sensor 9, and an outlet temperature sensor 11. Control module 13 is electrically connected to flue gas parameter sensing module, outlet temperature sensor 11, exhaust gas temperature sensor 14, variable frequency circulating pump 8, and inlet temperature sensor 9. The control module includes: The adjustment scheme generation module is used to generate an adjustment scheme for the basic cold source medium based on flue gas data; The optimization module is used to perform a first optimization on the basic cold source medium adjustment scheme, and then perform a second optimization on the first optimization process to obtain the second optimized adjustment scheme. The second optimized adjustment scheme is then output as the final target scheme. The variable frequency circulating pump operates at the speed determined by the final target scheme. The flue gas parameters include flue gas temperature parameters, flue gas flow rate parameters, basic inlet temperature parameters of the cold source medium, actual outlet temperature parameters of the cold source medium, and actual exhaust gas temperature parameters. The temperature sensor is used to collect flue gas temperature parameters, the flow sensor is used to collect flue gas flow parameters, and the exhaust gas temperature sensor is used to collect actual exhaust gas temperature parameters. The inlet temperature sensor is used to collect the basic inlet temperature parameters of the cold source medium, and the outlet temperature sensor is used to collect the actual outlet temperature parameters of the cold source medium. The control module is also electrically connected to an imported temperature sensor.

[0023] It should be noted that a gas-fired boiler is a commonly used heat energy conversion device. Fuel is burned in the furnace to produce high-temperature flue gas. After heat exchange, the high-temperature flue gas is discharged from the exhaust pipe. This part of the flue gas still contains some residual heat energy that has not been completely absorbed. In this embodiment, by setting a heat exchange component connected to the exhaust pipe, the flue gas flows through the heat exchange component to exchange heat with the cold source medium, transferring the heat energy to the cold source medium. The cold source medium carries the heat energy and finally flows to the downstream heat energy utilization device through the outlet pipe. The downstream heat energy utilization device includes a deaerator to reduce the amount of heating steam used in the deaerator, so as to further recover heat energy.

[0024] Specifically, the gas-fired boiler flue gas waste heat recovery and utilization system is applied in the field of gas-fired boiler equipment. It collects flue gas data through a flue gas parameter sensing module, a cold source medium supply module, an exhaust temperature sensor, and an outlet temperature sensor. Based on a basic cold source medium adjustment scheme generated by an adjustment scheme generation module, an optimization module is added. The first optimization unit of the optimization module performs a primary optimization of the basic cold source medium adjustment scheme, addressing the lack of temperature feedback based on actual exhaust temperature deviations, thereby improving the control accuracy of the cold source medium flow rate. The second optimization unit performs a secondary optimization of the primary optimization process, resolving the mismatch problem on the cold source side caused by only considering exhaust temperature deviations and not the actual outlet temperature deviation of the cold source medium. This achieves fine adjustment on the cold source medium side, thereby realizing dynamic matching between the cold source medium flow rate and the real-time heat load of the flue gas, thus improving the efficiency of flue gas waste heat recovery.

[0025] Please see Figure 2The diagram shown is a simplified structural diagram of the heat exchange component in this embodiment. The heat exchange component is a pulsating heat pipe heat exchange component, which includes a cold source chamber, a heat source chamber, and a pulsating heat pipe. The heat source chamber 17 is connected to the exhaust pipe 2. The heat source chamber 17 has an inlet 15 and an outlet 16, both of which are connected to the exhaust pipe 2. Part of the pulsating heat pipe passes through the cold source chamber 18, and another part passes through the heat source chamber 17. The cold source chamber 18 has a cold source medium inlet 19 and a cold source medium outlet 20. The cold source medium inlet 19 is connected to the inlet pipe, and the cold source medium outlet 20 is connected to the outlet pipe.

[0026] The heat exchange component operates as follows: flue gas in the exhaust duct enters the heat source chamber 17 through the inlet 15 and exchanges heat with the hot section of the pulsating heat pipe installed in the heat source chamber. After heat exchange, the flue gas returns to the exhaust duct 2 through the outlet 16. The cold source medium enters the cold source chamber 18 through the cold source medium inlet 19 and exchanges heat with the cold section of the pulsating heat pipe installed in the cold source chamber. After heat exchange, the cold source medium flows to the downstream thermal energy utilization device through the outlet pipe from the cold source medium outlet 20.

[0027] Specifically, the use of pulsed heat pipe heat exchange components results in a small temperature difference between the wall surface and the heat source, which can reduce the flue gas temperature and allow for full recovery of waste heat from the flue gas. Constructing a portion of the flue gas duct as a heat source chamber and inserting the pulsed heat pipes into the pipe wall can replace part of the economizer, significantly reducing steel consumption and investment costs. Since the flue gas and the cold source medium do not directly contact each other, even if the pulsed heat pipe leaks, the impact on the system is minimal, reducing operating and maintenance costs and failure rates. Separating the cold source chamber and heat source chamber, and achieving indirect heat exchange through the pulsed heat pipes, avoids direct contamination of the cold source medium by corrosive flue gas, improving system operational safety.

[0028] Specifically, the adjustment scheme generation module generates a basic cold source medium adjustment scheme based on flue gas data, including: The adjustment scheme generation module is based on Flue gas temperature parameters Flue gas flow parameters Target flue gas temperature parameters Basic inlet temperature parameters of cold source medium and Target outlet temperature parameter versus base flow rate Perform calculations. ,in, For the density of the flue gas, The specific heat capacity of flue gas at constant pressure. Density of the cold source medium This refers to the specific heat capacity of the cold source medium.

[0029] It is worth noting that the basic cold source medium adjustment scheme is a scheme that uses the basic flow rate value as the control parameter of the variable frequency circulating pump.

[0030] Specifically, the flue gas density refers to the mass of a unit volume of flue gas. It is obtained by collecting flue gas samples for component analysis and calculating the average molar mass of the flue gas based on the volume fraction and molar mass of each component. The flue gas specific heat capacity at constant pressure refers to the amount of heat required to raise the temperature of a unit mass of flue gas by 1°C under constant pressure. In this embodiment, the flue gas specific heat capacity at constant pressure is obtained by looking up a table of flue gas temperatures. The cold source medium density refers to the mass of a unit volume of cold source medium. The density of the cold source medium is obtained by looking up the cold source medium. The specific heat capacity of the cold source medium refers to the amount of heat required to raise the temperature of a unit mass of cold source medium by 1°C. It is obtained by looking up the properties of the cold source medium.

[0031] Please see Figure 3 As shown, this is a schematic diagram of the control module in Embodiment 1. The control module includes an adjustment scheme generation module and an optimization module. The adjustment scheme generation module is connected to the optimization module. The optimization module includes a first optimization unit and a second optimization unit. The first optimization unit and the second optimization unit are connected. The first optimization unit is used to perform a first optimization on the basic cold source medium adjustment scheme to obtain a first-optimized adjustment scheme. The second optimization unit is used to perform a second optimization on the first optimization process to obtain a second-optimized adjustment scheme.

[0032] Please see Figure 4 As shown, this is a logic diagram of the first optimization unit in this embodiment. The first optimization unit optimizes the basic cold source medium adjustment scheme once to obtain an optimized adjustment scheme, including: Based on actual smoke exhaust temperature parameters With the target flue gas temperature parameter The exhaust temperature deviation P is calculated and compared with the preset exhaust temperature deviation threshold P0, where: When P > P0, the basic cold source medium regulation scheme is optimized once. The optimization includes: performing incremental compensation calculation on the basic flow value according to the flue gas temperature deviation to obtain the optimized flow value, and replacing the basic flow value in the basic cold source medium regulation scheme with the optimized flow value to obtain the optimized regulation scheme. When P≤P0, the basic cold source medium regulation scheme is not optimized once, and the basic cold source medium regulation scheme is output as the optimized regulation scheme.

[0033] Specifically, the actual flue gas temperature parameter refers to the flue gas temperature measured downstream of the flue gas duct after heat exchange through the heat exchange components. The target flue gas temperature parameter refers to the target flue gas temperature value expected to be achieved by the system during steady-state operation, which is set at 130℃. The reason for this value is that this temperature is within a safe margin range of 10℃ to 20℃ above the acid dew point temperature of the flue gas at the tail of the gas boiler, which can effectively prevent low-temperature corrosion and ensure that the waste heat of the flue gas is fully recovered. The preset flue gas deviation threshold is the critical temperature difference value for determining whether the actual flue gas temperature parameter exceeds the allowable fluctuation range, which is set at 5℃. The reason for this value is that, according to heat transfer error analysis and engineering practice, when the actual flue gas temperature parameter deviates from the target flue gas temperature parameter by more than 5℃, it indicates that there is a significant mismatch between the flow rate of the cold source medium and the heat load of the flue gas. The incremental compensation calculation includes: based on the primary compensation coefficient K1 and the actual flue gas temperature parameter... Target flue gas temperature parameters Flue gas flow parameters Smoke density flue gas specific heat capacity at constant pressure Density of cold source medium Specific heat capacity of cold source medium Target outlet temperature parameters and the basic inlet temperature parameters of the cold source medium For basic flow value Perform calculations and set parameters. K1 is set to 0.8. The reason for this value is as follows: In thermal process control, if 100% full compensation is applied to the temperature deviation, the actuator may oscillate and the system may overshoot due to measurement noise and heat transfer lag. According to the principle of conservative control in engineering, an 80% partial compensation strategy is usually adopted to ensure that the flue gas temperature deviation converges within a limited adjustment period, while retaining a 20% margin to suppress the amplification of disturbances. Therefore, K1 is set to 0.8.

[0034] Specifically, the second optimization unit performs a second optimization on the first optimization process to obtain a second-optimized adjustment scheme, including: Based on the actual outlet temperature parameters of the cold source medium With the target outlet temperature parameter The outlet water temperature deviation is calculated, and the outlet water temperature deviation is... Deviation threshold from preset effluent A comparison was performed, including: when When performing the first optimization, a second optimization is performed. The second optimization includes: performing a correction and compensation calculation on the flow rate value after the first optimization based on the outlet water temperature deviation to obtain the flow rate value after the second optimization, and replacing the flow rate value after the first optimization in the adjustment scheme with the flow rate value after the second optimization to obtain the adjustment scheme after the second optimization. when At that time, the optimization process is not optimized a second time, but the adjustment scheme after the first optimization is output as the adjustment scheme after the second optimization.

[0035] Specifically, the actual outlet temperature parameter of the cold source medium refers to the outlet water temperature measured at the outlet pipe after the cold source medium has completed heat exchange through the heat exchange components. The target outlet temperature parameter refers to the desired temperature target value that the cold source medium is expected to achieve after passing through the heat exchange components, and is set to 85℃. The reason for this value is that this temperature is lower than the saturation temperature under the deaerator's working pressure, and can be used as the preheating temperature of the deaerator's inlet water, effectively reducing the amount of heating steam used by the deaerator. The preset outlet water deviation threshold refers to the critical temperature difference value used to determine whether the actual outlet temperature parameter of the cold source medium exceeds the allowable fluctuation range. The value is 3℃, and the reason for this value is as follows: When the actual outlet temperature parameter of the cold source medium is more than 3℃ higher than the target outlet temperature parameter, it indicates that the flow rate value after the first optimization is still too small, and the cold source medium is overheated in the heat exchanger. It is necessary to increase the flow rate through the second optimization unit to reduce the outlet temperature and increase the total heat exchange. When the actual outlet temperature is lower than the target value, the second optimization unit does not trigger the flow reduction command due to the heat on the flue gas side, so as to ensure that the minimum flow constraint of the lower limit constraint unit is executed first. The correction and compensation calculation includes: based on the secondary compensation coefficient K2 and the actual outlet temperature parameter of the cold source medium. Target outlet temperature parameters and the basic inlet temperature parameters of the cold source medium For the flow rate value after secondary optimization Perform calculations. The value of K2 is 0.3. The reason for this value is that in the cascade control structure, the secondary optimization unit, as the fine adjustment link of the inner loop, must have a lower response sensitivity than the coarse adjustment link of the outer loop formed by the primary optimization unit. Otherwise, the two loops will generate resonance overshoot due to the superposition of gains. According to the principle of "outer loop dominates and inner loop follows" in cascade PID tuning in control theory, the proportional gain of the inner loop is usually taken as 30% to 50% of that of the outer loop to form master-slave decoupling. In this embodiment, the primary compensation coefficient K1 is 0.8, so the secondary compensation coefficient K2 is calibrated according to 37.5% of the outer loop gain and is taken as 0.3. This ensures that the inner loop can quickly suppress the deviation of the outlet water temperature and avoids the pump speed oscillation caused by the inner loop responding too fast.

[0036] Specifically, the variable frequency circulating pump operates at a speed according to the final target scheme, including: The final flow rate value contained in the final target scheme is converted into a target speed command for the variable frequency circulating pump. The conversion is based on the flow-speed characteristic curve of the variable frequency circulating pump through linear interpolation to obtain the pump shaft speed setting value corresponding to the final flow rate value. The control module outputs the pump shaft speed setting value as an analog signal to the inverter drive unit of the variable frequency circulating pump. The inverter drive unit adjusts the motor power supply frequency according to the pump shaft speed setting value, so that the variable frequency circulating pump operates according to the final flow rate value, thereby actually delivering the cold source medium flow rate determined by the constrained adjustment scheme to the heat exchange components.

[0037] Example 2: Please see Figure 5 As shown, this is a schematic diagram of the control module in Embodiment 2. Unlike Embodiment 1, in this embodiment, the control module further includes a scheme constraint module. The scheme constraint module is used to apply flow constraints to the secondary optimized adjustment scheme to obtain a constrained adjustment scheme, and replace the content of the secondary optimized adjustment scheme with the content of the constrained adjustment scheme. The adjustment scheme generation module is connected to the optimization module, and the scheme constraint module is connected to the optimization module. The scheme constraint module includes a lower limit constraint unit and an upper limit constraint unit. The secondary optimized adjustment scheme includes a secondary optimized flow value. The lower limit constraint unit is used to set the constraint flow value according to the secondary optimized flow value in the secondary optimized adjustment scheme. The upper limit constraint unit is used to apply flow constraints to the secondary optimized adjustment scheme according to the constraint flow value to obtain a constrained adjustment scheme, and replace the content of the secondary optimized adjustment scheme with the content of the constrained adjustment scheme. The lower limit constraint unit and the upper limit constraint unit are connected.

[0038] Specifically, in this embodiment, the system also uses a scheme constraint module to constrain the flow rate of the secondary optimized adjustment scheme, thereby solving the problem of equipment damage risk caused by the flow rate value after secondary optimization exceeding the safe operating boundary of the equipment in the prior art, and realizing safe operation under double boundary protection; and by using a variable frequency circulating pump to operate at the speed according to the final target scheme, it solves the problem of insufficient waste heat recovery of flue gas caused by the disconnect between the flow rate of the cold source medium and the state of waste heat of flue gas in the prior art, thereby improving the efficiency of waste heat recovery of flue gas.

[0039] Please see Figure 6 As shown, this is a logic diagram of the lower limit constraint unit in this embodiment. The lower limit constraint unit sets the constraint flow value based on the secondary optimized flow value Qw2 in the secondary optimized adjustment scheme, including: The optimized flow rate value Qw2 is compared with the preset minimum flow rate Qmin, where: When Qw2 < Qmin, the preset minimum flow rate Qmin will be output as the constraint flow rate value Qy; When Qw2≥Qmin, the optimized flow value QW2 is output as the constraint flow value Qy.

[0040] Specifically, the preset minimum flow rate refers to the minimum flow rate limit for safe operation of the variable frequency circulating pump, which is set at 15t / h. The reason for this value is that this flow rate is the critical flow rate required to maintain the minimum turbulent state on the cold source side of the pulsating heat pipe in the heat exchange component. If it is lower than this value, it will cause the cold source medium to stagnate, local vaporization and heat exchange to deteriorate, and may even cause the cold source chamber to dry burn.

[0041] Specifically, the upper limit constraint unit applies flow constraints to the secondary optimization adjustment scheme based on the constraint flow value to obtain the constrained adjustment scheme, and replaces the content of the secondary optimization adjustment scheme with the content of the constrained adjustment scheme, including: The constrained flow rate value Qy is compared with the preset maximum flow rate Qmax, where: When Qy > Qmax, the preset maximum flow rate Qmax is output as the final flow rate value, and the second-optimized flow rate value in the second-optimized adjustment scheme is replaced with the final flow rate value to obtain the constrained adjustment scheme. The content of the second-optimized adjustment scheme is then replaced with the content of the constrained adjustment scheme. When Qy≤Qmax, the constraint flow value Qy is output as the final flow value, and the secondary optimized flow value in the secondary optimized adjustment scheme is replaced with the final flow value to obtain the constraint adjustment scheme. The content of the secondary optimized adjustment scheme is then replaced with the content of the constraint adjustment scheme.

[0042] Specifically, the preset maximum flow rate refers to the highest allowable flow rate limit of the variable frequency circulating pump and pipeline system, which is set at 80t / h. The reason for this value is that this flow rate is the maximum output flow rate of the variable frequency circulating pump under rated operating conditions. Exceeding this value will lead to pump overload, motor current exceeding limits, and accelerated pipeline erosion and corrosion.

[0043] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A waste heat recovery and utilization system for flue gas from a gas-fired boiler, characterized in that, include: The flue gas parameter sensing module includes a temperature sensor and a flow sensor. The temperature sensor and flow sensor are located inside the flue gas duct and upstream of the heat exchange component. A flue gas temperature sensor is located downstream of the heat exchange component. A cold source medium supply module, which is connected to a heat exchange component, includes an inlet pipe and a variable frequency circulating pump. An inlet temperature sensor is provided on the inlet pipe, and the variable frequency circulating pump is located on the inlet pipe. One end of the inlet pipe is connected to the cold source medium supply module, and the other end is connected to the heat exchange component. A heat exchange component is provided with an outlet pipe, an outlet temperature sensor is provided on the outlet pipe, and the outlet pipe is connected to a heat energy utilization device; The system collects flue gas data through a flue gas parameter sensing module, a cold source medium supply module, a flue gas temperature sensor, an inlet temperature sensor, and an outlet temperature sensor. The control module is electrically connected to the flue gas parameter sensing module, the outlet temperature sensor, the exhaust gas temperature sensor, the variable frequency circulating pump, and the inlet temperature sensor. The control module includes: The adjustment scheme generation module is used to generate an adjustment scheme for the basic cold source medium based on flue gas data; The optimization module is used to perform a first optimization on the basic cold source medium adjustment scheme, and then perform a second optimization on the first optimization process to obtain the second optimized adjustment scheme. The second optimized adjustment scheme is then output as the final target scheme. The variable frequency circulating pump operates at the speed according to the final target scheme.

2. The waste heat recovery and utilization system for gas-fired boiler flue gas according to claim 1, characterized in that, The flue gas parameters include flue gas temperature parameters, flue gas flow rate parameters, basic inlet temperature parameters of the cold source medium, actual outlet temperature parameters of the cold source medium, and actual exhaust gas temperature parameters. The temperature sensor is used to collect flue gas temperature parameters, the flow sensor is used to collect flue gas flow parameters, and the exhaust gas temperature sensor is used to collect actual exhaust gas temperature parameters. The inlet temperature sensor is used to collect the basic inlet temperature parameters of the cold source medium, and the outlet temperature sensor is used to collect the actual outlet temperature parameters of the cold source medium. The adjustment scheme generation module calculates the basic flow rate value based on the flue gas temperature parameter, flue gas flow rate parameter, target exhaust gas temperature parameter, basic inlet temperature parameter of the cold source medium, and target outlet temperature parameter, and outputs the basic flow rate value as the basic cold source medium adjustment scheme.

3. The waste heat recovery and utilization system for gas-fired boiler flue gas according to claim 2, characterized in that, The heat exchange component is a pulsating heat pipe heat exchange component, which includes a cold source chamber, a heat source chamber, and pulsating heat pipes. The heat source chamber is connected to the flue gas duct. Part of the pulsating heat pipe is installed in the cold source chamber, and another part is installed in the heat source chamber. The cold source chamber has a cold source medium inlet and a cold source medium outlet. The cold source medium inlet is connected to the inlet pipe, and the cold source medium outlet is connected to the outlet pipe.

4. The waste heat recovery system for gas-fired boiler flue gas according to claim 2, characterized in that, The optimization module includes a first optimization unit and a second optimization unit. The first optimization unit is used to perform a first optimization on the basic cold source medium adjustment scheme to obtain a first-optimized adjustment scheme. The second optimization unit is used to perform a second optimization on the first optimization process to obtain a second-optimized adjustment scheme.

5. The waste heat recovery and utilization system for flue gas from a gas-fired boiler according to claim 4, characterized in that, The first optimization unit performs a first-order optimization on the basic cold source medium adjustment scheme to obtain an optimized adjustment scheme, including: The exhaust temperature deviation is calculated based on the actual and target exhaust temperature parameters, and then compared with a preset exhaust temperature deviation threshold. When the flue gas temperature deviation is greater than the preset flue gas deviation threshold, the basic cold source medium regulation scheme is optimized once. The optimization includes: performing incremental compensation calculation on the basic flow value according to the flue gas temperature deviation to obtain the optimized flow value, and replacing the basic flow value in the basic cold source medium regulation scheme with the optimized flow value to obtain the optimized regulation scheme. When the flue gas temperature deviation is less than or equal to the preset flue gas deviation threshold, the basic cold source medium adjustment scheme will not be optimized once, and the basic cold source medium adjustment scheme will be output as the optimized adjustment scheme.

6. The waste heat recovery system for gas-fired boiler flue gas according to claim 5, characterized in that, The second optimization unit performs a second optimization on the first optimization process to obtain a second-optimized adjustment scheme, including: The outlet water temperature deviation is calculated based on the actual outlet temperature parameters of the cold source medium and the target outlet temperature parameters. The outlet water temperature deviation is then compared with a preset outlet water deviation threshold, where: When the outlet water temperature deviation is greater than the preset outlet water deviation threshold, the first optimization process is optimized again. The second optimization includes: performing a correction and compensation calculation on the flow rate value after the first optimization based on the outlet water temperature deviation to obtain the flow rate value after the second optimization, and replacing the flow rate value after the first optimization in the adjustment scheme after the first optimization with the flow rate value after the second optimization to obtain the adjustment scheme after the second optimization. When the outlet water temperature deviation is less than or equal to the preset outlet water deviation threshold, the first optimization process will not be optimized a second time, and the adjustment scheme after the first optimization will be output as the adjustment scheme after the second optimization.

7. The waste heat recovery system for gas-fired boiler flue gas according to claim 1, characterized in that, The control module also includes a scheme constraint module, which is used to impose flow constraints on the secondary optimization adjustment scheme to obtain a constrained adjustment scheme, and replace the content of the secondary optimization adjustment scheme with the content of the constrained adjustment scheme.

8. The waste heat recovery system for gas-fired boiler flue gas according to claim 7, characterized in that, The scheme constraint module includes a lower limit constraint unit and an upper limit constraint unit. The secondary optimization adjustment scheme includes a secondary optimization flow value. The lower limit constraint unit is used to set the constraint flow value according to the secondary optimization flow value in the secondary optimization adjustment scheme. The upper limit constraint unit is used to constrain the flow of the secondary optimization adjustment scheme according to the constraint flow value to obtain the constrained adjustment scheme, and replace the content of the secondary optimization adjustment scheme with the content of the constrained adjustment scheme.

9. The waste heat recovery system for gas-fired boiler flue gas according to claim 8, characterized in that, The lower limit constraint unit sets the constraint flow value based on the secondary optimized flow value in the secondary optimized adjustment scheme, including: The optimized flow rate value is compared with the preset minimum flow rate, where: When the flow rate after secondary optimization is less than the preset minimum flow rate, the preset minimum flow rate will be output as the constraint flow rate value. When the optimized flow rate is greater than or equal to the preset minimum flow rate, the optimized flow rate will be output as the constraint flow rate.

10. The waste heat recovery system for gas-fired boiler flue gas according to claim 9, characterized in that, The upper limit constraint unit applies flow constraints to the secondary optimization adjustment scheme based on the constraint flow value, obtains the constrained adjustment scheme, and replaces the content of the secondary optimization adjustment scheme with the content of the constrained adjustment scheme, including: The constrained flow rate value is compared with the preset maximum flow rate, where: When the constrained flow rate is greater than the preset maximum flow rate, the preset maximum flow rate is output as the final flow rate value, and the second-optimized flow rate value in the second-optimized adjustment scheme is replaced with the final flow rate value to obtain the constrained adjustment scheme. The content of the second-optimized adjustment scheme is then replaced with the content of the constrained adjustment scheme. When the constraint flow value is less than or equal to the preset maximum flow, the constraint flow value is output as the final flow value, and the secondary optimized flow value in the secondary optimized adjustment scheme is replaced with the final flow value to obtain the constraint adjustment scheme. The content of the secondary optimized adjustment scheme is then replaced with the content of the constraint adjustment scheme.

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