A carbonization furnace-based flue gas waste heat utilization system

Abstract

The present application relates to the technical field of waste heat recovery, and more particularly to a flue gas waste heat utilization system based on a carbonization furnace. It comprises a data acquisition module, a waste heat utilization module, a decay analysis module, an efficiency determination module, an efficiency control module, a control detection module and an optimization module. The system monitors the flue gas heat flow rate and particulate matter concentration in real time through the data acquisition module, and the waste heat utilization module intelligently formulates a gradient waste heat utilization scheme. The decay analysis module analyzes the stability of waste heat recovery rate and the performance decay rate. The efficiency determination module and the efficiency control module automatically generate and execute control strategies such as soot blowing based on the deviation of the soot accumulation rate from the preset value. The control detection module and the optimization module subsequently evaluate the performance after control, and start the optimization algorithm when the performance does not meet the standard. The present application realizes the monitoring and control of the waste heat recovery process, effectively improving the energy utilization efficiency and the system operation stability.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology, and in particular to a waste heat utilization system based on flue gas from a carbonization furnace. Background Technology

[0002] Currently, flue gas waste heat recovery systems based on carbonization furnaces typically include waste heat boilers, generator sets, and other devices, achieving energy recovery through heat exchange with high-temperature flue gas. However, existing technologies still have several significant problems in practical applications. First, the utilization methods of flue gas waste heat are often relatively simple, lacking an intelligent decision-making mechanism for graded and tiered utilization based on flue gas energy grade. This fails to achieve the optimal energy allocation principle of "temperature matching and tiered utilization," resulting in high-grade heat energy not being prioritized for high-efficiency power generation, leaving considerable room for improvement in overall energy utilization efficiency.

[0003] Secondly, high-temperature flue gas typically contains a certain concentration of particulate matter. When these particles flow through heat exchange equipment, they easily deposit and accumulate on the heated surfaces, creating additional thermal resistance and severely weakening heat exchange efficiency. This leads to a decline in the performance of the waste heat recovery system over time. Existing systems often use timed soot blowing for cleaning, lacking real-time perception and accurate judgment of the ash accumulation status and performance degradation. The frequency and intensity of cleaning operations often rely on experience, resulting in inconsistency. This can lead to two drawbacks: first, untimely cleaning leads to severe ash accumulation, causing the system to operate in an inefficient state for extended periods; second, excessively frequent cleaning not only wastes soot blowing media and exacerbates equipment wear but may also affect the stability of system operation due to frequent disturbances.

[0004] Therefore, there is an urgent need for a new type of waste heat utilization system and method for carbonization furnace flue gas, which can intelligently allocate energy utilization methods, monitor the system performance degradation status in real time, accurately diagnose ash accumulation problems, and then implement differentiated and efficient cleaning strategies to ultimately achieve intelligent maintenance and optimization of waste heat recovery efficiency and overcome the shortcomings of existing technologies.

[0005] Chinese Patent Publication No. CN104893745A discloses a waste heat utilization system for biomass carbonization furnace flue gas, including a carbonization furnace, a flue gas purification device, a flue gas cooling tower, and a composting and fermentation chamber. The carbonization furnace, flue gas purification device, and flue gas cooling tower are sequentially connected by a flue gas pipeline. The flue gas cooling tower and the composting and fermentation chamber are connected by a hot water return pipeline. Biomass is carbonized in the carbonization furnace, and the generated flue gas is purified by the flue gas purification device before entering the flue gas cooling tower to heat the circulating water in the water pipes inside the flue gas cooling tower. The circulating water in the water pipes inside the flue gas cooling tower enters the composting and fermentation chamber through the hot water return pipeline, providing heat for the composting and fermentation of livestock and poultry manure. This invention is the first to combine a carbonization furnace and organic fertilizer production together. The high-temperature flue gas generated by the carbonization furnace is used to heat the circulating water through the flue gas cooling tower, making the circulating water suitable for the growth of fermentation bacteria. The water is then transported to the rapid organic fertilizer system, promoting the improvement of organic fertilizer fermentation efficiency.

[0006] Therefore, it can be seen that the aforementioned biomass carbonization furnace flue gas waste heat utilization system has the following problems:

[0007] In the process of waste heat recovery from high-temperature flue gas, the concentration of particulate matter carried in the high-temperature flue gas was not taken into account. This would cause the particulate matter concentration in the high-temperature flue gas to adhere to the heat exchange surface, resulting in an increase in the ash ratio of the heat exchange area and a thicker ash accumulation. Consequently, the heat in the high-temperature flue gas could not be effectively recovered, and the waste heat recovery efficiency was unstable. Summary of the Invention

[0008] Therefore, the present invention provides a waste heat recovery system based on a carbonization furnace to overcome the problems in the prior art, such as the degradation of waste heat recovery performance and the accumulation of ash on the heat exchange surface due to changes in particulate matter concentration, which leads to the inability to fully utilize heat and unstable waste heat recovery efficiency.

[0009] To achieve the above objectives, the present invention provides a flue gas waste heat utilization system based on a carbonization furnace. It includes:

[0010] The data acquisition module is used to obtain the heat flow rate of the high-temperature flue gas after tar removal and the particulate matter concentration in the high-temperature flue gas.

[0011] Waste heat utilization module, which is used to determine the gradient utilization scheme of high-temperature flue gas based on the heat flow rate;

[0012] The attenuation analysis module is used to determine the stability of the waste heat recovery rate of the high-temperature flue gas flowing through the waste heat boiler based on the average change rate of particulate matter concentration in the high-temperature flue gas under the corresponding utilization scheme, and to calculate the performance attenuation rate of the waste heat recovery rate when the waste heat recovery rate is unstable.

[0013] The efficiency determination module is used to determine whether the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler meets the standard based on the performance decay rate, and to calculate the ash accumulation rate of the heat exchange surface of the waste heat boiler when the waste heat recovery efficiency does not meet the standard.

[0014] An efficiency control module is used to determine, based on the ash accumulation rate, the frequency of soot blowing to the heat exchange interface of the waste heat boiler to control the waste heat utilization module, and to obtain the maximum performance degradation rate after control.

[0015] The regulation detection module is used to determine whether the regulation is qualified based on the comparison result of the maximum performance decay rate and the target performance decay rate.

[0016] An optimization module is used to determine, based on the absolute decay difference between the maximum performance decay rate and the target performance decay rate, to increase the soot blowing pressure on the heat exchange surface in order to optimize the efficiency control module.

[0017] Furthermore, in response to a heat flow rate less than or equal to a preset heat flow rate, the waste heat utilization module determines a first utilization scheme to directly introduce high-temperature flue gas into the waste heat boiler to generate low-pressure steam to activate the carbonized material.

[0018] Furthermore, in response to a heat flow rate greater than a preset heat flow rate, the waste heat utilization module determines a second utilization scheme: first, the high-temperature flue gas is fed into a steam turbine to generate high-pressure steam for power generation; then, the high-temperature flue gas after the steam power generation is completed is fed into a waste heat boiler to generate low-pressure steam to activate the carbonized material.

[0019] Furthermore, the attenuation analysis module determines that the waste heat recovery rate of the high-temperature flue gas flowing through the waste heat boiler is unstable based on the absolute value of the average change rate of particulate matter concentration being greater than the absolute value of the preset average change rate of particulate matter, and calculates the performance attenuation rate of the waste heat recovery rate when the waste heat recovery rate is unstable.

[0020] Furthermore, the efficiency determination module determines that the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler is substandard in response to the performance decay rate during the waste heat recovery process being less than the preset performance decay rate, and calculates the ash accumulation rate of the heat exchange surface of the waste heat boiler when the waste heat recovery efficiency is substandard.

[0021] Furthermore, the efficiency control module determines to increase the soot blowing frequency of the waste heat boiler heat exchange interface in response to the absolute difference between the ash accumulation rate and the preset ash accumulation rate being less than or equal to the preset absolute difference.

[0022] Furthermore, the efficiency control module determines to increase the soot blowing frequency on the heat exchange interface of the waste heat boiler in response to the absolute difference between the ash accumulation rate and the preset ash accumulation rate being greater than the preset absolute difference, and obtains the maximum performance degradation rate after control.

[0023] Furthermore, the regulation detection module determines that the regulation is unqualified in response to the maximum performance decay rate being less than the target performance decay rate.

[0024] Furthermore, in response to the absolute decay difference between the maximum performance decay rate and the target performance decay rate being less than or equal to a preset absolute decay difference, the optimization module determines to increase the soot blowing pressure on the heat exchange surface by executing the efficiency control module.

[0025] Furthermore, in response to the absolute decay difference between the maximum performance decay rate and the target performance decay rate being greater than a preset absolute decay difference, the optimization module determines to increase the soot blowing pressure on the heat exchange surface by executing the efficiency control module.

[0026] Compared with the prior art, the beneficial effects of the present invention are that the present invention calculates the heat flow rate of high-temperature flue gas in real time and accurately through the data acquisition module, and intelligently selects the optimal gradient utilization scheme according to the heat flow rate, ensuring that high-grade heat energy is given priority for high-efficiency power generation, and low-grade heat energy is used for activation or drying, realizing temperature matching and cascade utilization of energy, minimizing heat energy waste, and significantly improving the overall energy utilization efficiency.

[0027] Furthermore, this invention monitors the rate of change of particulate matter concentration in real time through the attenuation analysis module and compares it with the preset average rate of change of particulate matter concentration obtained from historical stable data. It can accurately identify the unstable state of the system and calculate the performance attenuation rate before the waste heat recovery rate shows a significant decline. This enables the calculation of the performance attenuation rate before the waste heat recovery efficiency fails to meet the requirements, providing a key decision-making basis for subsequent maintenance.

[0028] Furthermore, this invention transforms the fuzzy problem of heat exchange surface contamination into a quantifiable indicator by calculating the ash accumulation rate on the heat exchange surface of the waste heat boiler. Based on the absolute difference between the ash accumulation rate and the preset ash accumulation rate, a differentiated soot blowing strategy is formulated, avoiding the blindness of traditional timed soot blowing. This effectively keeps the heat exchange surface clean and reduces the consumption of soot blowing media, achieving a balance between energy saving and high efficiency, improving heat exchange efficiency, and enhancing the stability of waste heat recovery.

[0029] Furthermore, this invention determines whether the regulation is qualified by comparing the maximum performance decay rate after regulation with the target decay rate. Under unqualified conditions, different levels of optimization strategies are formulated based on the absolute decay difference between the maximum decay rate and the target decay rate. This enables the waste heat recovery system to not only have a primary efficiency regulation, but also to activate a secondary optimization module when the regulation effect is poor, forming a two-layer closed-loop optimization mechanism. This allows the waste heat recovery system to cope with different ash accumulation conditions. Even if the primary regulation strategy has limited effect, the system performance can be restored to the target range through a more powerful optimization strategy, ensuring the long-term stability and reliability of the waste heat recovery system.

[0030] Furthermore, this invention achieves fully automated intelligent operation, reducing reliance on manual labor and operating costs. From state perception and analysis to execution and control, the entire process is completed automatically by the system without human intervention. This not only reduces reliance on operator experience and avoids human error, but also greatly reduces the workload of daily inspections and adjustments, realizing unmanned and intelligent operation of the device and effectively reducing the system's operation and maintenance costs. Attached Figure Description

[0031] Figure 1 This is a block diagram showing the module connection of a flue gas waste heat utilization system based on a carbonization furnace according to an embodiment of the present invention.

[0032] Figure 2 This is a logic block diagram illustrating how the gradient utilization method of high-temperature flue gas is determined based on heat flow rate in an embodiment of the present invention.

[0033] Figure 3 This is a logic block diagram illustrating the determination of whether the waste heat recovery rate is stable based on the average change rate of particulate matter concentration in an embodiment of the present invention.

[0034] Figure 4 This is a logic block diagram of an embodiment of the present invention for determining whether the waste heat recovery efficiency meets the standard based on the performance decay rate;

[0035] Figure 5 This is a logic block diagram of an embodiment of the present invention for determining a corresponding control strategy based on the absolute difference between the ash accumulation rate and the preset ash accumulation rate;

[0036] Figure 6 This is a logic block diagram of an embodiment of the present invention for determining whether the regulation is qualified based on the maximum performance decay rate after regulation.

[0037] Figure 7 This is a logic block diagram illustrating how an embodiment of the present invention determines the corresponding optimization strategy based on the absolute attenuation difference between the maximum performance attenuation rate and the target attenuation rate. Detailed Implementation

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Please see Figure 1 As shown, Figure 1 This is a block diagram showing the module connection of a flue gas waste heat utilization system based on a carbonization furnace according to an embodiment of the present invention.

[0042] This invention relates to a flue gas waste heat utilization system based on a carbonization furnace, comprising:

[0043] The data acquisition module is used to obtain the heat flow rate of the high-temperature flue gas after tar removal and the particulate matter concentration in the high-temperature flue gas.

[0044] The waste heat utilization module is connected to the data acquisition module and is used to determine the gradient utilization scheme of the high-temperature flue gas based on the heat flow rate of the high-temperature flue gas after tar removal.

[0045] The attenuation analysis module is connected to the data acquisition module and the waste heat utilization module respectively. It is used to determine the stability of the waste heat recovery rate of the high-temperature flue gas flowing through the waste heat boiler based on the average change rate of particulate matter concentration in the high-temperature flue gas under the corresponding utilization scheme, and to calculate the performance attenuation rate of the waste heat recovery rate when the waste heat recovery rate is unstable.

[0046] An efficiency determination module, which is connected to the attenuation analysis module, is used to determine whether the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler meets the standard based on the performance attenuation rate during the waste heat recovery process, and to calculate the ash accumulation rate of the heat exchange surface of the waste heat boiler if it does not meet the standard.

[0047] An efficiency control module, which is connected to the waste heat utilization module and the efficiency determination module, is used to determine, based on the ash accumulation rate, to increase the soot blowing frequency on the heat exchange interface of the waste heat boiler to control the waste heat utilization module, and to obtain the maximum performance degradation rate after control.

[0048] A control and detection module, which is connected to the efficiency control module, is used to determine, based on the absolute decay difference between the maximum performance decay rate and the target performance decay rate, to increase the soot blowing pressure on the heat exchange surface in order to optimize the efficiency control module.

[0049] An optimization module, which is connected to the regulation detection module and the efficiency regulation module respectively, is used to determine the optimization strategy for the efficiency regulation module based on the difference between the maximum performance decay rate and the maximum performance decay rate threshold.

[0050] In this embodiment of the invention, the data acquisition module monitors the high-temperature flue gas after tar removal in real time using a smoke temperature sensor and a smoke flow sensor. It acquires the temperature value and mass flow rate of the high-temperature flue gas after tar removal, and finally obtains the heat flux of the high-temperature flue gas using a formula.

[0051] ;

[0052] In the formula, The heat flux of the high-temperature flue gas. The mass flow rate of high-temperature flue gas through the pipeline. The exhaust temperature of the high-temperature flue gas after tar removal. For ambient temperature, This represents the average isobaric specific heat capacity of the high-temperature flue gas.

[0053] In this embodiment of the invention, the average isobaric specific heat capacity Cp is determined in the following way: First, the volume fraction of each major component in the flue gas is obtained by a flue gas analyzer; then, based on the isobaric specific heat capacity value of each component at temperature T, a weighted average calculation is performed with the volume fraction as the weight, and finally the average isobaric specific heat capacity Cp is obtained.

[0054] In this embodiment of the invention, for a carbonization furnace using biomass as raw material, the flue gas composition after tar removal is relatively stable. Based on the calculation results of a large number of typical operating conditions using the weighted average method, the range of the average isobaric specific heat capacity Cp is as follows: The preferred value is 1.12 kJ / kg·℃.

[0055] In this embodiment of the invention, the data acquisition module obtains the particulate matter concentration value in the high-temperature flue gas after tar removal using a laser dust collector.

[0056] Please see Figure 2 As shown, Figure 2 This is a logic block diagram illustrating how the gradient utilization method of high-temperature flue gas is determined based on heat flow rate in an embodiment of the present invention.

[0057] Specifically, the waste heat utilization module determines a gradient utilization scheme for the high-temperature flue gas based on a comparison between the heat flow rate of the high-temperature flue gas after tar removal and a preset heat flow rate.

[0058] If the heat flow rate is less than or equal to the preset heat flow rate, then the first utilization scheme is determined to be to directly pass the high-temperature flue gas into the waste heat boiler to generate low-pressure steam to activate the carbonized material.

[0059] If the heat flow rate is greater than the preset heat flow rate, then a second utilization scheme is determined, in which the high-temperature flue gas is first fed into a steam turbine to generate high-pressure steam for power generation, and then the high-temperature flue gas after the steam power generation is completed is fed into a waste heat boiler to generate low-pressure steam to activate the carbonized material.

[0060] The preset heat flow rate is the average heat flow rate of several historical high-temperature flue gas events. The historical heat flow rate of 50 historical high-temperature flue gas events is taken, and the average heat flow rate of the historical heat flow rate is calculated to obtain the preset heat flow rate.

[0061] In this embodiment of the invention, the preset heat flux rate is in the range of 2MW-4MW, and the preferred value is 3MW. The preferred range and preferred value of the preset heat flux rate can be determined according to the actual situation, and are not specifically limited here.

[0062] Specifically, this invention uses a data acquisition module to accurately calculate the heat flow rate of high-temperature flue gas in real time, and intelligently selects the optimal gradient utilization scheme based on the heat flow rate. This ensures that high-grade heat energy is prioritized for high-efficiency power generation, while low-grade heat energy is used for activation or drying. This achieves temperature matching and tiered utilization of energy, minimizes heat energy waste, and significantly improves overall energy utilization efficiency.

[0063] Please see Figure 3 As shown, Figure 3 This is a logic block diagram for determining whether the waste heat recovery rate is stable based on the average change rate of particulate matter concentration, according to an embodiment of the present invention.

[0064] Specifically, under the corresponding utilization scheme, the attenuation analysis module determines the stability of the waste heat recovery rate of the high-temperature flue gas flowing through the waste heat boiler based on the comparison between the absolute value of the average change rate of particulate matter concentration in the high-temperature flue gas and the preset absolute value of the average change rate of particulate matter concentration. When the waste heat recovery rate is unstable, it calculates the performance degradation rate of the waste heat utilization rate.

[0065] If the absolute value of the average change rate of particulate matter concentration is less than or equal to the absolute value of the preset average change rate of particulate matter concentration, then the waste heat recovery rate is determined to be in a stable state.

[0066] If the absolute value of the average change rate of particulate matter concentration is greater than the absolute value of the preset average change rate of particulate matter concentration, then the waste heat recovery rate is determined to be unstable.

[0067] The absolute value of the average change rate of particulate matter concentration is determined based on a single combustion cycle of the carbonization furnace. During a single combustion cycle of the carbonization furnace, the particulate matter concentration in the high-temperature flue gas is monitored at 30-minute intervals to obtain the monitored particulate matter concentration value. The absolute difference between consecutive monitoring windows is calculated to obtain the change in particulate matter concentration. Finally, the ratio of the change in particulate matter concentration to the interval is calculated to obtain the absolute value of the average change rate of particulate matter concentration.

[0068] The preset average change rate of particulate matter concentration is determined based on the single combustion cycle of the carbonization furnace. Within the single combustion cycle of the carbonization furnace, the single combustion cycle is divided into several monitoring windows with an interval of 30 minutes. The particulate matter concentration value monitored each time is recorded, and the absolute difference between the continuous monitoring windows is calculated to obtain the particulate matter concentration change under several monitoring windows. Finally, the ratio of the single particulate matter concentration change to the interval is calculated to obtain the average change rate of particulate matter. The maximum average change rate of particulate matter in the continuous monitoring window is selected as the absolute value of the preset particulate matter concentration change rate.

[0069] In this embodiment of the invention, the absolute value of the preset average change rate of particulate matter concentration ranges from 0.04 mg / m³. 3 / min-0.06mg / m 3 / min, the preferred value in this invention is 0.05 mg / m 3 / min, the preferred range and preferred value of the preset average change rate of particulate matter concentration can be determined according to the actual situation, and are not specifically limited here.

[0070] Specifically, under the condition of determining the corresponding utilization scheme, the waste heat recovery rate is unstable. For the high-temperature flue gas flowing through the waste heat boiler, the performance decay rate is calculated. In practical applications, firstly, the specific enthalpy of the steam produced after the high-temperature flue gas is introduced into the waste heat boiler is calculated as the difference between the specific enthalpy of the steam produced and the specific enthalpy of the boiler feedwater. Then, the product of the specific enthalpy difference and the boiler feedwater volume is calculated to obtain the actual heat recovered by the waste heat boiler per unit time. The difference between the temperature of the high-temperature flue gas entering the waste heat boiler and the saturation temperature of the produced steam is selected as the theoretical heat transfer temperature difference. Then, the ratio of the actual recovered heat to the theoretical heat transfer temperature difference is calculated to obtain a relative performance index characterizing the instantaneous heat transfer performance of the boiler. Finally, the ratio of the change value of the relative performance index under two adjacent monitoring time windows to that under a single monitoring time window is calculated to obtain the performance decay rate.

[0071] Please see Figure 4 As shown, Figure 4 This is a logic block diagram illustrating how the waste heat recovery efficiency is determined based on the performance degradation rate in an embodiment of the present invention.

[0072] Specifically, this invention monitors the rate of change of particulate matter concentration in real time through an attenuation analysis module and compares it with the preset average rate of change of particulate matter concentration obtained from historical stable data. It can accurately identify the unstable state of the system and calculate the performance attenuation rate before the waste heat recovery rate shows a significant decline. This enables the calculation of the performance attenuation rate before the waste heat recovery efficiency fails to meet the requirements, providing a key decision-making basis for subsequent maintenance.

[0073] Specifically, under the condition of a determined performance degradation rate, the efficiency determination module determines whether the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler meets the standard based on the comparison result of the performance degradation rate during the waste heat recovery process and the preset performance degradation rate, and calculates the ash accumulation rate of the heat exchange interface of the waste heat boiler if it does not meet the standard.

[0074] If the performance degradation rate is greater than or equal to the preset performance degradation rate, then the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler is determined to meet the standard.

[0075] If the performance degradation rate is less than the preset performance degradation rate, then it is determined that the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler is substandard.

[0076] In this embodiment of the invention, the preset performance decay rate ranges from -1% / h to -3% / h, and the preferred value is -2% / h. The preferred range and preferred value of the preset performance decay rate can be determined according to the actual situation, and are not specifically limited here.

[0077] In this embodiment of the invention, under the condition that the waste heat recovery efficiency is not up to standard, the real-time ash accumulation rate of the waste heat boiler heat exchange surface is obtained based on the performance decay rate. In practical applications, firstly, the total heat transfer coefficient of the waste heat boiler is calculated as the initial heat transfer coefficient under the initial use state, and the reciprocal of the initial heat transfer coefficient is calculated to obtain the initial thermal resistance. Then, the actual heat recovered per unit time is calculated based on the real-time monitored feedwater flow and steam enthalpy of the waste heat boiler. Next, the difference between the high-temperature flue gas inlet temperature and the steam saturation temperature is selected as the theoretical heat transfer temperature difference, and the ratio of the actual recovered heat to the theoretical heat transfer temperature difference is calculated to obtain the relative performance index proportional to the current initial heat transfer coefficient. The difference between the current total thermal resistance and the initial thermal resistance is calculated to obtain the increase in ash accumulation thermal resistance. Subsequently, the product of the increase in ash accumulation thermal resistance and the ash thermal conductivity is calculated to obtain the estimated ash layer thickness. Finally, the ash accumulation rate is calculated as the ratio of the change in ash layer thickness under two adjacent monitoring time windows to the duration of the time window.

[0078] The thermal conductivity of the ash is an empirical constant determined based on historical data and experimental analysis of ash samples. For biomass carbonization flue gas ash, the value ranges from 0.05 W / (m·K) to 0.15 W / (m·K). The preferred value in this invention is 0.1 W / (m·K). The preferred range and preferred value can be determined according to the actual situation and are not specifically limited here.

[0079] Please see Figure 5 As shown, Figure 5 This is a logic block diagram illustrating how the present invention determines the corresponding control strategy based on the absolute difference between the ash accumulation rate and the preset ash accumulation rate.

[0080] Specifically, given a fixed ash accumulation rate, the efficiency control module determines a control strategy for the heat exchange interface of the waste heat boiler based on a comparison of the absolute difference between the ash accumulation rate and a preset ash accumulation rate, and obtains the maximum performance degradation rate after control.

[0081] If the absolute difference is less than or equal to the preset absolute difference, then the first control strategy for the heat exchange interface of the waste heat boiler is determined.

[0082] If the absolute difference is greater than the preset absolute difference, then a second control strategy for the heat exchange interface of the waste heat boiler is determined.

[0083] In this embodiment of the invention, the preset ash accumulation rate ranges from 0.04 mm / h to 0.06 mm / h, and the preferred value is 0.05 mm / h. The preferred range and preferred value of the preset ash accumulation rate can be determined according to the actual situation, and are not specifically limited here.

[0084] In this embodiment of the invention, the preset absolute difference ranges from 0.009 mm / h to 0.011 mm / h, and the preferred value is 0.01 mm / h. The preferred range and preferred value of the preset absolute difference can be determined according to the actual situation, and are not specifically limited here.

[0085] In this embodiment of the invention, the absolute difference is less than or equal to a preset absolute difference, indicating that the ash accumulation rate of the waste heat boiler heat exchange surface is close to the preset ash accumulation rate. The first control strategy is to increase the soot blowing frequency of the heat exchange interface, increasing the soot blowing frequency to 0.6 to 0.8 times the rated soot blowing frequency. The preferred value in this invention is 0.7 times, that is, increasing the soot blowing frequency to 0.7 times the rated soot blowing frequency. For example, if the rated soot blowing frequency is 9 hours / time, the increased soot blowing frequency is 6.3 hours / time. This is used to blow away the ash accumulation on the heat exchange surface of the waste heat boiler, reduce the ash thickness on the heat exchange surface, improve heat exchange efficiency, thereby increasing waste heat recovery efficiency, reducing the waste of heat in high-temperature flue gas, and enhancing the stability of waste heat recovery.

[0086] In this embodiment of the invention, the absolute difference is greater than the preset absolute difference, indicating that the ash accumulation rate of the waste heat boiler heat exchange surface is significantly different from the preset ash accumulation rate. The second control strategy is to increase the soot blowing frequency of the heat exchange interface, increasing the soot blowing frequency to 0.4 to 0.6 times the rated soot blowing frequency. The preferred value in this invention is 0.5 times, that is, increasing the soot blowing frequency to 0.5 times the rated soot blowing frequency. For example, if the rated soot blowing frequency is 9 hours / time, the increased soot blowing frequency is 4.5 hours / time. This is used to blow away the ash accumulation on the heat exchange surface of the waste heat boiler, reduce the ash thickness on the heat exchange surface, improve heat exchange efficiency, thereby increasing waste heat recovery efficiency, reducing the waste of heat in high-temperature flue gas, and enhancing the stability of waste heat recovery.

[0087] The rated soot blowing frequency is the conventional soot blowing parameter for the heat exchange surface recommended during the system design phase based on the boiler model, heat exchange surface layout, and initial design flue gas conditions.

[0088] Specifically, this invention transforms the fuzzy problem of heat exchange surface contamination into a quantifiable indicator by calculating the ash accumulation rate on the heat exchange surface of the waste heat boiler. Based on the absolute difference between the ash accumulation rate and the preset ash accumulation rate, a differentiated soot blowing strategy is formulated, avoiding the blindness of traditional timed soot blowing. This effectively keeps the heat exchange surface clean and reduces the consumption of soot blowing media, achieving a balance between energy saving and high efficiency, improving heat exchange efficiency, and enhancing the stability of waste heat recovery.

[0089] Specifically, after regulating the heat exchange interface of the waste heat boiler, the maximum performance degradation rate after regulation is calculated. In practical applications, firstly, the difference between the specific enthalpy of the steam produced after the high-temperature flue gas is introduced into the waste heat boiler and the specific enthalpy of the boiler feedwater is calculated. Then, the product of the specific enthalpy difference and the boiler feedwater flow rate is calculated to obtain the actual heat recovered by the waste heat boiler per unit time after regulation. The difference between the temperature of the high-temperature flue gas entering the waste heat boiler and the saturation temperature of the produced steam is selected as the theoretical heat transfer temperature difference. Then, the ratio of the actual recovered heat to the theoretical heat transfer temperature difference is calculated to obtain a relative performance index characterizing the instantaneous heat transfer performance of the boiler. Finally, the ratio of the change value of the relative performance index under continuous monitoring time window to that under a single monitoring time window is calculated to obtain several performance degradation rates after regulation. Since the performance degradation rate is a negative value, the closer its value is to zero, the more stable the performance. Therefore, the maximum value among the several performance degradation rates is taken as the maximum performance degradation rate after regulation.

[0090] Please see Figure 6 As shown, Figure 6 This is a logic block diagram illustrating how an embodiment of the present invention determines whether the regulation is qualified based on the maximum performance decay rate after regulation.

[0091] Specifically, the regulation detection module determines whether the regulation is qualified based on the comparison between the maximum performance decay rate and the target performance decay rate.

[0092] If the maximum performance degradation rate is less than the target performance degradation rate, the regulation is determined to be unqualified.

[0093] If the maximum performance degradation rate is greater than or equal to the target performance degradation rate, then the regulation is deemed qualified.

[0094] In this embodiment of the invention, the target performance degradation rate ranges from -0.8% / h to -1% / h, and the preferred value is -0.9% / h. The preferred range and preferred value of the maximum performance degradation rate can be determined according to the actual situation, and are not specifically limited here.

[0095] Please see Figure 7 As shown, Figure 7 This is a logic block diagram illustrating how an embodiment of the present invention determines the corresponding optimization strategy based on the absolute attenuation difference between the maximum performance attenuation rate and the target attenuation rate.

[0096] Specifically, when the control strategy is determined to be unqualified, the optimization module determines an optimization strategy for the efficiency control module based on the comparison of the absolute decay difference between the maximum performance decay rate and the target performance decay rate.

[0097] If the absolute attenuation difference is less than or equal to the preset absolute attenuation difference, then the first optimization strategy for the efficiency control module is determined.

[0098] If the absolute attenuation difference is greater than the preset absolute attenuation difference, then a second optimization strategy for the efficiency control module is determined.

[0099] In this invention, the preset absolute attenuation difference is the difference between the maximum performance attenuation rate and the target performance attenuation rate, and the value range is 0.08% / h to 0.1% / h. The preferred value in this invention is 0.09% / h. The preferred range and preferred value of the absolute attenuation difference can be determined according to the actual situation, and are not specifically limited here.

[0100] In this embodiment of the invention, the absolute attenuation difference is less than the preset absolute attenuation difference, indicating that the deviation between the maximum performance attenuation rate after regulation and the target performance attenuation rate is small. The first optimization strategy is to increase the soot blowing pressure to 1.1 to 1.3 times the rated soot blowing pressure. The preferred value in this invention is 1.2 times, that is, to increase the soot blowing pressure to 1.2 times the rated soot blowing pressure. For example, if the rated soot blowing pressure is 1.5 MPa, the increased soot blowing pressure is 1.8 MPa. This is used to blow away the ash accumulation on the heat exchange surface of the waste heat boiler, reduce the ash thickness on the heat exchange surface, improve heat exchange efficiency, thereby increasing the waste heat recovery efficiency, reducing the waste of heat in high-temperature flue gas, and enhancing the stability of waste heat recovery.

[0101] In this embodiment of the invention, the absolute attenuation difference is greater than the preset absolute attenuation difference, indicating that the deviation between the maximum performance attenuation rate after regulation and the target performance attenuation rate is large. The second optimization strategy is to increase the soot blowing pressure to 1.4 to 1.6 times the rated soot blowing pressure. The preferred value in this invention is 1.5 times, that is, to increase the soot blowing pressure to 1.5 times the rated soot blowing pressure. For example, if the rated soot blowing pressure is 1.5 MPa, the increased soot blowing pressure is 2.25 MPa. This is used to blow away the ash accumulation on the heat exchange surface of the waste heat boiler, reduce the ash thickness on the heat exchange surface, improve heat exchange efficiency, thereby increasing the waste heat recovery efficiency, reducing the waste of heat in high-temperature flue gas, and enhancing the stability of waste heat recovery.

[0102] The rated soot blowing pressure is the conventional soot blowing parameter for the heat exchange surface recommended during the system design phase based on the boiler model, heat exchange surface layout, and initial design flue gas conditions.

[0103] Specifically, this invention determines whether the regulation is qualified by comparing the maximum performance decay rate after regulation with the target decay rate. Under unqualified conditions, different levels of optimization strategies are formulated based on the absolute decay difference between the maximum decay rate and the target decay rate. This enables the waste heat recovery system to not only have primary efficiency regulation, but also to activate a secondary optimization module when the regulation effect is poor, forming a two-layer closed-loop optimization mechanism. This allows the waste heat recovery system to cope with different ash accumulation conditions. Even if the primary regulation strategy has limited effect, the system performance can be restored to the target range through a more powerful optimization strategy, ensuring the long-term stability and reliability of the waste heat recovery system.

[0104] 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 flue gas waste heat utilization system based on a carbonization furnace, characterized in that, include, The data acquisition module is used to obtain the heat flow rate of the high-temperature flue gas after tar removal and the particulate matter concentration in the high-temperature flue gas. Waste heat utilization module, which is used to determine the gradient utilization scheme of high-temperature flue gas based on the heat flow rate; The attenuation analysis module is used to determine the stability of the waste heat recovery rate of the high-temperature flue gas flowing through the waste heat boiler based on the average change rate of particulate matter concentration in the high-temperature flue gas under the corresponding utilization scheme, and to calculate the performance attenuation rate of the waste heat recovery rate when the waste heat recovery rate is unstable. The efficiency determination module is used to determine whether the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler meets the standard based on the performance decay rate, and to calculate the ash accumulation rate of the heat exchange surface of the waste heat boiler when the waste heat recovery efficiency does not meet the standard. An efficiency control module is used to determine, based on the ash accumulation rate, the frequency of soot blowing to the heat exchange interface of the waste heat boiler to control the waste heat utilization module, and to obtain the maximum performance degradation rate after control. The regulation detection module is used to determine whether the regulation is qualified based on the comparison result of the maximum performance decay rate and the target performance decay rate. An optimization module is used to determine, based on the absolute decay difference between the maximum performance decay rate and the target performance decay rate, to increase the soot blowing pressure on the heat exchange surface in order to optimize the efficiency control module.

2. The flue gas waste heat utilization system based on a carbonization furnace according to claim 1, characterized in that, The waste heat utilization module responds to a heat flow rate less than or equal to a preset heat flow rate by determining a first utilization scheme, which involves directly introducing high-temperature flue gas into a waste heat boiler to generate low-pressure steam to activate the carbonized material.

3. The flue gas waste heat utilization system based on a carbonization furnace according to claim 2, characterized in that, The waste heat utilization module responds to the heat flow rate being greater than the preset heat flow rate by determining the second utilization scheme: first, the high-temperature flue gas is fed into a steam turbine to generate high-pressure steam for power generation, and then the high-temperature flue gas after the steam power generation is completed is fed into a waste heat boiler to generate low-pressure steam to activate the carbonized material.

4. The flue gas waste heat utilization system based on a carbonization furnace according to claim 3, characterized in that, The attenuation analysis module determines that the waste heat recovery rate of the high-temperature flue gas flowing through the waste heat boiler is unstable based on the absolute value of the average change rate of particulate matter concentration being greater than the absolute value of the preset average change rate of particulate matter, and calculates the performance attenuation rate of the waste heat recovery rate when the waste heat recovery rate is unstable.

5. The flue gas waste heat utilization system based on a carbonization furnace according to claim 4, characterized in that, The efficiency determination module determines that the waste heat recovery efficiency of the high-temperature flue gas flowing through the waste heat boiler is substandard when the performance decay rate during the waste heat recovery process is less than the preset performance decay rate, and calculates the ash accumulation rate of the heat exchange surface of the waste heat boiler when the waste heat recovery efficiency is substandard.

6. The flue gas waste heat utilization system based on a carbonization furnace according to claim 5, characterized in that, The efficiency control module determines to increase the soot blowing frequency at the heat exchange interface of the waste heat boiler in response to the absolute difference between the ash accumulation rate and the preset ash accumulation rate being less than or equal to the preset absolute difference.

7. The flue gas waste heat utilization system based on a carbonization furnace according to claim 6, characterized in that, The efficiency control module determines to increase the soot blowing frequency to the heat exchange interface of the waste heat boiler when the absolute difference between the ash accumulation rate and the preset ash accumulation rate is greater than the preset absolute difference, and obtains the maximum performance degradation rate after the control.

8. The flue gas waste heat utilization system based on a carbonization furnace according to claim 7, characterized in that, The regulation detection module determines that the regulation is unqualified when the maximum performance decay rate is less than the target performance decay rate.

9. The flue gas waste heat utilization system based on a carbonization furnace according to claim 8, characterized in that, The optimization module determines that the efficiency control module increases the soot blowing pressure on the heat exchange surface in response to the absolute decay difference between the maximum performance decay rate and the target performance decay rate being less than or equal to a preset absolute decay difference.

10. The flue gas waste heat utilization system based on a carbonization furnace according to claim 9, characterized in that, The optimization module determines that, in response to the absolute decay difference between the maximum performance decay rate and the target performance decay rate being greater than a preset absolute decay difference, it will increase the soot blowing pressure on the heat exchange surface by executing the efficiency control module.

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