Gradient utilization method for waste heat of kiln

Abstract

The invention relates to the technical field of ceramic production waste heat utilization, in particular to a kiln waste heat gradient utilization method which comprises the steps that after a ceramic tile enters a cooling zone from a firing zone, the preset cooling duration of a cooling section is determined according to the thickness of the ceramic tile, and after the preset cooling duration is over, hot air is extracted according to the preset heat extraction rate and the preset extraction amount; judging whether the extraction of the waste heat meets a preset standard or not according to the thermal deformation characterization value of the ceramic tile; when the thermal deformation characterization value is larger than or equal to a second preset thermal deformation characterization value, it is judged that extraction of the waste heat does not conform to a preset standard, and an extraction adjustment strategy when extraction of the waste heat does not conform to the preset standard is determined according to the audio frequency energy change rate of the ceramic tile within the preset frequency band; and according to the utilization grade and the processing strategy determined by the hot air utilization evaluation value, gradient utilization is conducted on the extracted hot air. The waste heat recovery efficiency of the kiln is improved.

Description

Technical Field

[0001] This invention relates to the field of waste heat utilization technology in ceramic production, and in particular to a method for the cascade utilization of waste heat from kilns. Background Technology

[0002] A tunnel kiln is generally a long, straight passage with fixed kiln walls and a kiln roof on both sides and top. Kiln cars run on tracks laid at the bottom, loading the fired products. Kiln cars enter and exit the kiln sequentially at the tail end. The kiln body forms fixed preheating and cooling zones, commonly referred to as the "three zones" of a tunnel kiln. The waste heat in the preheating zone, also called kiln head flue gas waste heat, cannot be used directly because it contains a large amount of corrosive flue gas. The waste heat in the cooling zone, also called kiln tail waste heat, is clean and reliable, mainly derived from the heat discharged after the products pass through the firing zone. The cooling zone is further divided into a rapid cooling section, a strong cooling section, and a cooling section. The temperature of the hot air in the rapid cooling section is approximately 300℃, the temperature of the hot air in the strong cooling section is approximately 200℃, and the temperature of the air in the cooling section is approximately 60℃~100℃. The rapid cooling and strong cooling sections are collectively referred to as the cooling section, and the hot air in the cooling section, i.e., the cooling hot air, has a temperature of approximately 200℃.

[0003] The high-temperature flue gas generated by combustion flows along the tunnel towards the kiln head in the chimney at the front of the tunnel kiln or under the action of the induced draft fan, gradually preheating the products entering the kiln and forming the preheating zone of the tunnel kiln. The middle of the tunnel kiln is the firing zone, where cold air is blown into the kiln tail to cool the products in the latter part of the kiln. After the products are heated, the blown-out cold air is extracted and sent to the drying kiln as a heat source for drying the bricks; this part constitutes the cooling zone of the tunnel kiln. Brick tunnel kilns use solid, liquid, and gaseous fuels. However, current waste heat utilization technologies are mostly relatively simple, usually directly extracting hot air from the cooling section for drying and other processes, lacking precise control over the quality of the hot air and the impact of the extraction process on the products.

[0004] Chinese Patent Application Publication No. CN115060085A discloses a method and system for utilizing waste heat from a kiln. The method includes: Step S1, exchanging heat between the hot flue gas discharged from the preheating zone of the kiln and air through heat exchanger A to obtain primary heat exchange flue gas and primary heating air; Step S2, introducing the cooling hot air discharged from the cooling section of the kiln and the primary heating air into the drying kiln to dry the brick blanks in the drying kiln, and discharging the drying kiln tail gas from the drying kiln; Step S3, exchanging heat between the primary heat exchange flue gas and hot air from the cooling section of the kiln through heat exchanger B to obtain secondary heat exchange flue gas and primary heating and cooling section hot air; Step S4, introducing the drying kiln tail gas and the primary heating and cooling section hot air into a burner for heating.

[0005] It can be seen that the above technical solution only recovers waste heat through a fixed process, without considering the impact of waste heat extraction on the cracking and deformation of ceramics, thus resulting in low waste heat recovery efficiency. Summary of the Invention

[0006] Therefore, the present invention provides a method for the cascade utilization of waste heat from kilns, which overcomes the problem of low waste heat recovery efficiency in the prior art, which only recovers waste heat through a fixed process and does not consider the impact of waste heat extraction on the cracking and deformation of ceramics.

[0007] To achieve the above objectives, the present invention provides a method for the cascade utilization of waste heat from kilns, comprising: After the flat rectangular ceramic tile enters the cooling zone from the firing zone, the preset cooling time of the cooling section is determined according to the thickness of the ceramic tile. During the preset cooling time, the temperature is reduced only by natural heat dissipation from the kiln body. After the preset cooling time is over, hot air is extracted according to the preset heat extraction rate and preset extraction amount. Infrared images of the tiles after heat extraction are obtained, and the thermal deformation characterization value of the tiles is calculated. Based on the thermal deformation characterization value of the tiles, it is determined whether the extraction of residual heat meets the preset standard. When the thermal deformation characterization value is greater than or equal to the first preset thermal deformation characterization value and less than the second preset thermal deformation characterization value, it is determined that the extraction of residual heat meets the preset standard, and the extraction of residual heat meets the preset standard again based on the sound velocity attenuation gradient of the ceramic tile. When the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, it is determined that the extraction of residual heat does not meet the preset standard, and the extraction adjustment strategy is determined according to the sound frequency energy change rate of the ceramic tile in the preset frequency band when the extraction of residual heat does not meet the preset standard. Based on the utilization level and treatment strategy determined by the hot air utilization evaluation value, the extracted hot air is utilized in a tiered manner.

[0008] Furthermore, the process of determining whether the extraction of residual heat meets the preset standard based on the thermal deformation characterization value of the ceramic tile includes: The thermal deformation characterization value is compared with the first preset thermal deformation characterization value and the second preset thermal deformation characterization value respectively; If the thermal deformation characterization value is less than the first preset thermal deformation characterization value, it is determined that the extraction of waste heat meets the preset standard, and the utilization level of the waste heat is determined according to the hot air utilization evaluation value and the corresponding treatment strategy is determined. If the thermal deformation characterization value is greater than or equal to the first preset thermal deformation characterization value and less than the second preset thermal deformation characterization value, then it is determined that the extraction of residual heat meets the preset standard, and the extraction of residual heat meets the preset standard again based on the sound velocity attenuation gradient of the ceramic tile. If the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, it is determined that the extraction of residual heat does not meet the preset standard, and the extraction adjustment strategy is determined according to the rate of change of the sound frequency energy of the ceramic tile in the preset frequency band when the extraction of residual heat does not meet the preset standard.

[0009] Furthermore, the process of obtaining the thermal deformation characterization value of the ceramic tile includes: Obtain an infrared image of the surface of the ceramic tile after heat extraction, and obtain the grayscale value of each pixel; Calculate the standard deviation of the grayscale value and record it as the thermal deformation characterization value of the ceramic tile.

[0010] Furthermore, the process of determining whether the extraction of residual heat does not meet the preset standard based on the sound velocity attenuation gradient of the ceramic tile includes: The sound speed attenuation gradient is compared with the preset sound speed attenuation gradient; If the sound velocity attenuation gradient is greater than or equal to the preset sound velocity attenuation gradient, it is determined that the extraction of waste heat does not meet the preset standard, and the preset cooling time is increased according to the difference between the sound velocity attenuation gradient and the preset sound velocity attenuation gradient.

[0011] Furthermore, the process of obtaining the sound velocity attenuation gradient of the tile includes: The first penetration time of the ultrasonic wave through the ceramic tile is obtained after the tile enters the cooling zone from the firing zone and begins to dissipate heat naturally. The ratio of the thickness of the ceramic tile to the first penetration time is calculated and denoted as the first sound velocity. After the hot air extraction is completed, the second penetration time of the ultrasonic wave through the tile is obtained, and the ratio of the tile thickness to the second penetration time is calculated and denoted as the second speed of sound. Calculate the difference between the second sound speed and the first sound speed to obtain the sound speed difference; The ratio of the absolute value of the sound velocity difference to the thickness of the tile is denoted as the sound velocity attenuation gradient of the tile.

[0012] Furthermore, several duration adjustment methods are provided for increasing the preset cooling time, among which, If the sound velocity attenuation gradient difference is less than the first preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using the first adjustment coefficient. If the sound velocity attenuation gradient difference is greater than or equal to the first preset sound velocity attenuation gradient difference and less than the second preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using the second adjustment coefficient. If the sound velocity attenuation gradient difference is greater than or equal to the second preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using the third adjustment coefficient. The sound speed attenuation gradient difference is the difference between the sound speed attenuation gradient and the preset sound speed attenuation gradient.

[0013] Furthermore, based on the rate of change of acoustic energy of the ceramic tile within a preset frequency band, an extraction adjustment strategy is determined when the extraction of waste heat does not meet the preset standard. If the rate of change of acoustic energy is less than the preset rate of change of acoustic energy, the preset heat extraction rate is reduced according to the difference between the preset rate of change of acoustic energy and the preset rate of change of acoustic energy. If the rate of change of sound frequency energy is greater than or equal to the preset rate of change of sound frequency energy, the heat extraction is immediately stopped and the air supply is started. The rate of change of the acoustic energy of the ceramic tile within the preset frequency band is determined by the first acoustic energy of the preset frequency band before cooling and the second acoustic energy of the preset frequency band after heat extraction.

[0014] Furthermore, the reduction in the preset heat extraction rate is positively correlated with the difference between the preset acoustic energy change rate and the acoustic energy change rate.

[0015] Furthermore, the utilization level of the hot air is determined based on the hot air utilization evaluation value, wherein, If the hot air utilization evaluation value is less than the first preset hot air utilization threshold, then the hot air is determined to be in the first utilization level; If the hot air utilization evaluation value is greater than or equal to the first preset hot air utilization threshold and less than the second preset hot air utilization threshold, then the hot air is determined to be in the second utilization level. If the hot air utilization evaluation value is greater than or equal to the second preset hot air utilization threshold, then the hot air is determined to be in the third utilization level. The hot air utilization evaluation value is determined by the hot air temperature, ambient temperature, and hot air extraction flow rate.

[0016] Furthermore, a corresponding processing strategy is determined based on the utilization level of the hot air, wherein, When the hot air is at the first utilization level, the hot air is filtered and then fed into the heating network through a heat exchanger for heating of the plant area. When the hot air is in the second utilization level, the hot air is filtered and then sent to the drying kiln to dry the ceramic tiles; When the hot air is at the third utilization level, the hot air is filtered and then sent to the firing zone for combustion support.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: By determining the preset cooling time based on the tile thickness, this invention achieves the adaptation of heat extraction parameters to product characteristics, reducing the thermal shock of cooling to the tile; simultaneously, it constructs a multi-dimensional quality monitoring and dynamic control closed loop based on the thermal deformation characterization value reflecting the surface warping deformation of the tile, combined with the sound velocity attenuation gradient and sound frequency energy change rate reflecting the changes in the internal structure of the tile. Through graded judgment and targeted adjustment, it ensures that waste heat extraction is always carried out under the premise of ensuring tile quality; furthermore, based on the utilization evaluation values ​​of parameters such as hot air temperature and flow rate, different grades of waste heat are accurately matched to suitable scenarios such as combustion, drying, and heating, thereby achieving efficient tiered utilization of waste heat.

[0018] Furthermore, this invention compares the thermal deformation characterization value with first and second preset values. When the thermal deformation characterization value is less than the first preset value, it directly enters the hot air utilization stage, reducing redundant detection. When the thermal deformation characterization value is in the middle range, the sound velocity gradient is activated for secondary verification to avoid misjudgment. When the thermal deformation characterization value is greater than or equal to the second preset value, the control strategy is triggered. This judgment method can accurately distinguish the degree of impact of the heat extraction process on the quality of the tiles, avoiding the judgment error of a single standard, and providing a clear basis for subsequent waste heat utilization level classification or heat extraction strategy adjustment.

[0019] Furthermore, this invention clarifies that the thermal deformation characterization value is obtained through the standard deviation of the grayscale value of the infrared image. The external image can intuitively reflect the uniformity of the temperature distribution on the surface of the tile. The smaller the standard deviation of the grayscale value, the more uniform the temperature distribution and the lower the risk of thermal deformation; conversely, the higher the risk of thermal deformation. This avoids the subjectivity of human judgment and thus improves the reliability of the assessment.

[0020] Furthermore, this invention overcomes the limitations of a single thermal deformation index by introducing a sound velocity attenuation gradient for secondary determination when the thermal deformation characterization value is in the middle range. By comparing the sound velocity attenuation gradient with a preset value, the impact of the heat extraction process on the internal structure of the tile is further identified, and the preset cooling time is adjusted accordingly, thereby ensuring the quality of the tile.

[0021] Furthermore, by setting up multi-level adjustment methods for increasing the cooling time, the present invention achieves precise control over the magnitude of the increase in cooling time.

[0022] Furthermore, when the thermal deformation characterization value is determined to be substandard, the present invention formulates an extraction and adjustment strategy based on the rate of change of acoustic energy within a preset frequency band. The change of acoustic energy of the tile reflects the damage to the material caused by thermal stress. By reducing the extraction rate or stopping the extraction and supplying air in a graded manner, the quality risks in the extraction process are responded to, thereby avoiding quality problems such as cracking and deformation of the tile due to extraction.

[0023] Furthermore, this invention uses evaluation values ​​to classify utilization levels, making the classification more scientific. That is, high evaluation values ​​correspond to high-grade hot air, and low evaluation values ​​correspond to low-grade hot air. This classification method provides a basis for subsequent tiered utilization, ensuring that hot air of different qualities is allocated to the most suitable use, avoiding the problem of high-grade waste heat being inefficiently utilized or low-grade waste heat failing to meet the application requirements, thereby improving the efficiency of waste heat utilization. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for cascaded utilization of waste heat from a kiln, as described in an embodiment of the present invention. Figure 2 This is a flowchart illustrating an embodiment of the present invention for determining whether the extraction of residual heat meets a preset standard based on the thermal deformation characterization value of the ceramic tile; Figure 3 This is a flowchart illustrating the secondary determination of whether the extraction of waste heat meets the preset standard in an embodiment of the present invention. Figure 4 This is a flowchart illustrating the extraction adjustment strategy when the extraction of waste heat does not meet the preset standard, as described in an embodiment of the present invention. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] It should be noted that the data in this embodiment are all derived from a comprehensive analysis and evaluation of historical test data and corresponding historical test results from the three months prior to this test. Those skilled in the art will understand that the method described in this invention can determine the above-mentioned parameters in the following ways: selecting the value with the highest proportion based on the data distribution as the preset standard parameter; using weighted summation to obtain the value as the preset standard parameter; substituting each historical data point into a specific formula and using the value obtained by that formula as the preset standard parameter; or other selection methods, as long as the method described in this invention can clearly define different specific situations in the single-item judgment process through the obtained values.

[0028] Please see Figure 1 , Figure 2 , Figure 3 as well as Figure 4The flowcharts shown are respectively: a flowchart of the kiln waste heat cascade utilization method according to an embodiment of the present invention; a flowchart of determining whether the extraction of waste heat meets the preset standard based on the thermal deformation characterization value of the ceramic tile according to an embodiment of the present invention; a flowchart of a second determination of whether the extraction of waste heat meets the preset standard according to an embodiment of the present invention; and a flowchart of the extraction adjustment strategy when it is determined that the extraction of waste heat does not meet the preset standard according to an embodiment of the present invention.

[0029] This invention provides a method for the cascade utilization of waste heat from kilns, comprising: Step S1: After the flat rectangular ceramic tile (thickness range of 5mm-20mm) enters the cooling zone from the firing zone, the preset cooling time of the cooling section is determined to be 15 minutes based on the thickness of the ceramic tile (10mm). During the preset cooling time, cooling is achieved solely through natural heat dissipation from the kiln body. After the preset cooling time is completed, the heat is extracted at a preset rate of 200m³ / h. 3 / h and preset extraction volume 80m 3 Extract hot air; Step S2: Obtain an infrared image of the tile after heat extraction, calculate the thermal deformation characterization value of the tile, and determine whether the extraction of residual heat meets the preset standard based on the thermal deformation characterization value of the tile. Step S3: When the thermal deformation characterization value is greater than or equal to the first preset thermal deformation characterization value and less than the second preset thermal deformation characterization value, it is determined that the extraction of residual heat meets the preset standard, and the extraction of residual heat meets the preset standard again based on the sound velocity attenuation gradient of the ceramic tile. Step S4: When the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, it is determined that the extraction of residual heat does not meet the preset standard, and the extraction adjustment strategy when the extraction of residual heat does not meet the preset standard is determined according to the sound frequency energy change rate of the ceramic tile in the preset frequency band. Step S5: Based on the utilization level and treatment strategy determined by the hot air utilization evaluation value, the extracted hot air is utilized in stages.

[0030] In this embodiment, the first preset thermal deformation characterization value is less than the second preset thermal deformation characterization value.

[0031] In this embodiment, the hot air is formed by heating the air inside the kiln with the sensible heat released by the ceramic itself.

[0032] It should be noted that the data in this embodiment are all results obtained through preliminary experiments before this test using the method described in this invention. Each preset value can be adjusted according to the specific application, as long as the method described in this invention can clearly define different specific situations in the single-item judgment process through the acquired values. The preset values ​​set in this embodiment are all obtained from preliminary experiments, including the correction coefficients, which were also selected through experimental verification.

[0033] Specifically, the thicker the tile, the slower the internal heat conduction, requiring a longer time for natural heat dissipation through the kiln. In this embodiment, the preset cooling time is 15 minutes for tiles with a thickness of 5mm-10mm and 25 minutes for tiles with a thickness of 11mm-20mm.

[0034] Specifically, the process of determining whether the extraction of residual heat meets the preset standard based on the thermal deformation characterization value of the ceramic tile includes: The thermal deformation characterization value is compared with the first preset thermal deformation characterization value 15 and the second preset thermal deformation characterization value 30, respectively. If the thermal deformation characterization value is less than the first preset thermal deformation characterization value, it is determined that the extraction of waste heat meets the preset standard, and the utilization level of the waste heat is determined according to the hot air utilization evaluation value and the corresponding treatment strategy is determined. If the thermal deformation characterization value is greater than or equal to the first preset thermal deformation characterization value and less than the second preset thermal deformation characterization value, then it is determined that the extraction of residual heat meets the preset standard, and the extraction of residual heat meets the preset standard again based on the sound velocity attenuation gradient of the ceramic tile. If the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, it is determined that the extraction of residual heat does not meet the preset standard, and the extraction adjustment strategy is determined according to the rate of change of the sound frequency energy of the ceramic tile in the preset frequency band when the extraction of residual heat does not meet the preset standard.

[0035] Specifically, the first preset thermal deformation characterization value ranges from [10, 20], and the second preset thermal deformation characterization value ranges from [25, 35]. Preferably, the first preset thermal deformation characterization value is selected as 15, and the second preset thermal deformation characterization value is selected as 30.

[0036] Specifically, the larger the standard deviation of the gray value, the more uneven the surface temperature distribution of the tile, and the higher the risk of thermal deformation.

[0037] Specifically, when the thermal deformation characterization value is less than the first preset thermal deformation characterization value, the degree of thermal deformation of the tile is small, with no obvious external deformation or internal hidden damage, and has no substantial impact on product quality. Therefore, it is directly judged to meet the standard, and the treatment strategy can be prioritized according to the hot air utilization level to ensure the efficiency of waste heat utilization. When the thermal deformation characterization value is in the middle range, although it does not obviously exceed the standard, there may be hidden quality risks. At this time, a secondary judgment is required through the sound velocity attenuation gradient to ensure that the standard is confirmed without ignoring hidden defects. When the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, the tile has shown significant thermal deformation and is judged to be non-compliant with the standard. Then, an adjustment strategy is determined based on the sound frequency energy change rate to prevent the damage from expanding.

[0038] Specifically, the process of obtaining the thermal deformation characterization value of the ceramic tile includes: Obtain an infrared image of the surface of the ceramic tile after heat extraction, and obtain the grayscale value of each pixel; Calculate the standard deviation of the grayscale value and record it as the thermal deformation characterization value of the ceramic tile.

[0039] Specifically, the process of determining whether the extraction of waste heat meets the preset standard based on the sound velocity attenuation gradient of the ceramic tile includes: The sound velocity attenuation gradient is compared with the preset sound velocity attenuation gradient of 0.6 m / (s·mm); If the sound velocity attenuation gradient is less than the preset sound velocity attenuation gradient, it is determined that the extraction of waste heat meets the preset standard, and the utilization level of the waste heat is determined according to the hot air utilization evaluation value and the corresponding treatment strategy is determined. If the sound velocity attenuation gradient is greater than or equal to the preset sound velocity attenuation gradient, it is determined that the extraction of waste heat does not meet the preset standard, and the preset cooling time is increased according to the difference between the sound velocity attenuation gradient and the preset sound velocity attenuation gradient.

[0040] In this embodiment, the preset sound velocity attenuation gradient is 0.6 m / (s·mm), but the above value is not limited to this. Those skilled in the art can adjust the above value according to actual needs. The lower the sound velocity attenuation gradient, the lower the internal density of the ceramic tile.

[0041] Specifically, the process of obtaining the sound velocity attenuation gradient of the tile includes: The ultrasonic detector is used to obtain the first penetration time of the ultrasonic waves through the ceramic tile after it enters the cooling zone from the firing zone and before it begins to dissipate heat naturally. The ratio of the thickness of the ceramic tile to the first penetration time is calculated and recorded as the first sound velocity. After the hot air extraction is completed, the second penetration time of the ultrasonic wave through the tile is obtained, and the ratio of the tile thickness to the second penetration time is calculated and denoted as the second speed of sound. Calculate the difference between the second sound speed and the first sound speed to obtain the sound speed difference; The ratio of the absolute value of the sound velocity difference to the thickness of the tile is denoted as the sound velocity attenuation gradient of the tile.

[0042] Specifically, there are several duration adjustment methods for increasing the preset cooling time, among which... If the sound velocity attenuation gradient difference is less than the first preset sound velocity attenuation gradient difference of 0.25m / (s·mm), then the preset cooling time is increased to the corresponding value using the first adjustment coefficient of 1.02. If the sound velocity attenuation gradient difference is greater than or equal to the first preset sound velocity attenuation gradient difference and less than the second preset sound velocity attenuation gradient difference of 0.45m / (s·mm), then the preset cooling time is increased to the corresponding value using the second adjustment coefficient of 1.04. If the sound velocity attenuation gradient difference is greater than or equal to the second preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using a third adjustment coefficient of 1.06. The sound speed attenuation gradient difference is the difference between the sound speed attenuation gradient and the preset sound speed attenuation gradient.

[0043] Specifically, based on the rate of change of acoustic energy of the ceramic tile within a preset frequency band of 100-300kHz, an adjustment strategy is determined when the extraction of waste heat does not meet the preset standard. If the rate of change of acoustic energy is less than 25% of the preset rate of change of acoustic energy, then the preset heat extraction rate is reduced according to the difference between the preset rate of change of acoustic energy and the preset rate of change of acoustic energy. If the rate of change of sound frequency energy is greater than or equal to the preset rate of change of sound frequency energy, the heat extraction is immediately stopped and the air supply is started. In this embodiment, the preset audio frequency energy change rate is selected as 25%, but the above value is not limited to this. Those skilled in the art can adjust the above value according to actual needs.

[0044] Specifically, the rate of change of sound frequency energy essentially characterizes the degree of damage evolution of the microstructure inside the ceramic tile under thermal stress, manifested as enhanced sound wave scattering effect caused by the generation and propagation of microcracks. When ultrasound (100–300kHz) penetrates the ceramic tile, its energy attenuation mainly stems from the scattering and absorption of sound waves by internal material defects (cracks). If the rate of residual heat extraction is too rapid during cooling, thermal stress will be generated inside the ceramic tile due to a sudden increase in temperature, triggering accelerated crack propagation. This propagation significantly increases the scattering interface of sound waves, resulting in a substantial reduction in sound wave energy during propagation.

[0045] The process of obtaining the rate of change of the audio frequency energy includes: After the tiles move from the firing zone into the cooling zone and before they begin to dissipate heat naturally, a high-frequency microphone is installed in the kiln observation window to collect the sound signals of the tiles in a preset frequency band of 100-300kHz. The energy of the collected sound signals in this frequency band is calculated, which is the first sound energy. After the hot air extraction operation is completed, the same high-frequency microphone and the same installation position as the one used to obtain the first audio energy are used to collect the audio signal of the tile in the preset frequency band of 100-300kHz again. The energy of the collected audio signal is calculated, which is the second audio energy. The absolute value of the difference between the second audio frequency energy and the first audio frequency energy is obtained, and then the ratio of the absolute value to the first audio frequency energy is obtained, which is the rate of change of audio frequency energy.

[0046] Specifically, the reduction in the preset heat extraction rate is positively correlated with the difference between the preset acoustic energy change rate and the acoustic energy change rate. The positive correlation can be linear or nonlinear. The slope of the linear positive correlation is not specifically limited. It can be understood that the greater the difference between the preset acoustic energy change rate and the acoustic energy change rate, the greater the reduction in the preset heat extraction rate.

[0047] Specifically, the utilization level of hot air is determined based on the hot air utilization evaluation value, wherein, If the hot air utilization evaluation value is less than the first preset hot air utilization threshold of 0.35, then the hot air is determined to be in the first utilization level; If the hot air utilization evaluation value is greater than or equal to the first preset hot air utilization threshold and less than the second preset hot air utilization threshold of 0.63, then the hot air is determined to be in the second utilization level. If the hot air utilization evaluation value is greater than or equal to the second preset hot air utilization threshold, then the hot air is determined to be in the third utilization level. The hot air utilization evaluation value is determined by the hot air temperature, ambient temperature, and hot air extraction flow rate.

[0048] The hot air utilization evaluation value is calculated using the following formula:

[0049] In the formula, Q represents the hot air utilization evaluation value, and T h T represents the hot air temperature; T0 represents the ambient temperature; T max T represents the highest temperature of the hot air. max =500℃; F represents the hot air extraction flow rate; F max This indicates the maximum hot air extraction flow rate, set to F. max =600m 3 / h.

[0050] In this embodiment, the first preset hot air utilization threshold is selected as 0.35 and the second preset hot air utilization threshold is selected as 0.63. However, the above values ​​are not limited to these values, and those skilled in the art can adjust the above values ​​according to actual needs.

[0051] The utilization value of hot air depends on the energy grade (temperature difference) and the total energy (flow rate): the higher the temperature and the greater the flow rate, the more waste heat can be utilized, and the higher the evaluation value.

[0052] Specifically, a corresponding processing strategy is determined based on the utilization level of the hot air, wherein, When the hot air is at the first utilization level, the hot air is filtered and then fed into the heating network through a heat exchanger for heating of the plant area. When the hot air is in the second utilization level, the hot air is filtered and then sent to the drying kiln to dry the ceramic tiles; When the hot air is at the third utilization level, the hot air is filtered and then sent to the firing zone for combustion support.

[0053] Specifically, the first utilization level corresponds to a lower grade and a limited total amount of hot air energy, which is suitable for scenarios where temperature requirements are not high. The second level of hot air utilization has a medium energy grade and total volume, which matches the needs of the tile drying process. The drying kiln requires hot air to remove moisture from the tile body. The temperature and flow rate of this level of hot air can meet the drying efficiency requirements without causing waste due to excess energy, which is a precise match between process and energy. The third-grade hot air has the highest energy grade and abundant quantity, making it suitable for combustion-supporting scenarios in the firing zone where temperature requirements are stringent. Combustion requires high-temperature hot air (above 300℃) to assist fuel combustion, and the high-grade thermal energy of the hot air can be directly utilized to improve combustion efficiency and reduce fuel consumption.

[0054] 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.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for cascade utilization of waste heat from kilns, characterized in that, include: After the flat rectangular ceramic tile enters the cooling zone from the firing zone, the preset cooling time of the cooling section is determined according to the thickness of the ceramic tile. During the preset cooling time, the temperature is reduced only by natural heat dissipation from the kiln body. After the preset cooling time is over, hot air is extracted according to the preset heat extraction rate and preset extraction amount. Infrared images of the tiles after heat extraction are obtained, and the thermal deformation characterization value of the tiles is calculated. Based on the thermal deformation characterization value of the tiles, it is determined whether the extraction of residual heat meets the preset standard. When the thermal deformation characterization value is greater than or equal to the first preset thermal deformation characterization value and less than the second preset thermal deformation characterization value, it is determined that the extraction of residual heat meets the preset standard, and the extraction of residual heat meets the preset standard again based on the sound velocity attenuation gradient of the ceramic tile. When the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, it is determined that the extraction of residual heat does not meet the preset standard, and the extraction adjustment strategy is determined according to the sound frequency energy change rate of the ceramic tile in the preset frequency band when the extraction of residual heat does not meet the preset standard. Based on the utilization level and treatment strategy determined by the hot air utilization evaluation value, the extracted hot air is utilized in a tiered manner. The process of determining whether the extraction of residual heat meets the preset standard based on the thermal deformation characterization value of the ceramic tile includes: The thermal deformation characterization value is compared with the first preset thermal deformation characterization value and the second preset thermal deformation characterization value respectively; If the thermal deformation characterization value is less than the first preset thermal deformation characterization value, it is determined that the extraction of waste heat meets the preset standard, and the utilization level of the waste heat is determined according to the hot air utilization evaluation value and the corresponding treatment strategy is determined. If the thermal deformation characterization value is greater than or equal to the first preset thermal deformation characterization value and less than the second preset thermal deformation characterization value, then it is determined that the extraction of residual heat meets the preset standard, and the extraction of residual heat meets the preset standard again based on the sound velocity attenuation gradient of the ceramic tile. If the thermal deformation characterization value is greater than or equal to the second preset thermal deformation characterization value, it is determined that the extraction of residual heat does not meet the preset standard, and the extraction adjustment strategy when the extraction of residual heat does not meet the preset standard is determined according to the rate of change of the sound frequency energy of the ceramic tile in the preset frequency band. The process of obtaining the thermal deformation characterization value of the ceramic tile includes: Obtain an infrared image of the surface of the ceramic tile after heat extraction, and obtain the grayscale value of each pixel; Calculate the standard deviation of the grayscale value and record it as the thermal deformation characterization value of the ceramic tile.

2. The method for cascade utilization of kiln waste heat according to claim 1, characterized in that, The process of determining whether the extraction of residual heat does not meet the preset standard based on the sound velocity attenuation gradient of the ceramic tile includes: The sound speed attenuation gradient is compared with the preset sound speed attenuation gradient; If the sound velocity attenuation gradient is greater than or equal to the preset sound velocity attenuation gradient, it is determined that the extraction of waste heat does not meet the preset standard, and the preset cooling time is increased according to the difference between the sound velocity attenuation gradient and the preset sound velocity attenuation gradient.

3. The method for cascade utilization of kiln waste heat according to claim 2, characterized in that, The process of obtaining the sound velocity attenuation gradient of the ceramic tile includes: The first penetration time of the ultrasonic wave through the ceramic tile is obtained after the tile enters the cooling zone from the firing zone and begins to dissipate heat naturally. The ratio of the thickness of the ceramic tile to the first penetration time is calculated and denoted as the first sound velocity. After the hot air extraction is completed, the second penetration time of the ultrasonic wave through the tile is obtained, and the ratio of the tile thickness to the second penetration time is calculated and denoted as the second speed of sound. Calculate the difference between the second sound speed and the first sound speed to obtain the sound speed difference; The ratio of the absolute value of the sound velocity difference to the thickness of the tile is denoted as the sound velocity attenuation gradient of the tile.

4. The method for cascade utilization of kiln waste heat according to claim 3, characterized in that, Several duration adjustment methods are provided to accommodate the increase in the preset cooling time, among which, If the sound velocity attenuation gradient difference is less than the first preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using the first adjustment coefficient. If the sound velocity attenuation gradient difference is greater than or equal to the first preset sound velocity attenuation gradient difference and less than the second preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using the second adjustment coefficient. If the sound velocity attenuation gradient difference is greater than or equal to the second preset sound velocity attenuation gradient difference, then the preset cooling time is increased to the corresponding value using the third adjustment coefficient. The sound speed attenuation gradient difference is the difference between the sound speed attenuation gradient and the preset sound speed attenuation gradient.

5. The method for cascade utilization of kiln waste heat according to claim 4, characterized in that, The extraction adjustment strategy is determined based on the rate of change of acoustic energy of the ceramic tile within a preset frequency band, when the extraction of waste heat does not meet the preset standard. If the rate of change of acoustic energy is less than the preset rate of change of acoustic energy, the preset heat extraction rate is reduced according to the difference between the preset rate of change of acoustic energy and the preset rate of change of acoustic energy. If the rate of change of sound frequency energy is greater than or equal to the preset rate of change of sound frequency energy, the heat extraction is immediately stopped and the air supply is started. The rate of change of the acoustic energy of the ceramic tile within the preset frequency band is determined by the first acoustic energy of the preset frequency band before cooling and the second acoustic energy of the preset frequency band after heat extraction.

6. The method for cascade utilization of kiln waste heat according to claim 5, characterized in that, The reduction in the preset heat extraction rate is positively correlated with the difference between the preset acoustic energy change rate and the acoustic energy change rate.

7. The method for cascade utilization of kiln waste heat according to claim 6, characterized in that, The utilization level of hot air is determined based on the hot air utilization evaluation value, among which, If the hot air utilization evaluation value is less than the first preset hot air utilization threshold, then the hot air is determined to be in the first utilization level; If the hot air utilization evaluation value is greater than or equal to the first preset hot air utilization threshold and less than the second preset hot air utilization threshold, then the hot air is determined to be in the second utilization level. If the hot air utilization evaluation value is greater than or equal to the second preset hot air utilization threshold, then the hot air is determined to be in the third utilization level. The hot air utilization evaluation value is determined by the hot air temperature, ambient temperature, and hot air extraction flow rate.

8. The method for cascade utilization of kiln waste heat according to claim 7, characterized in that, The corresponding processing strategy is determined based on the utilization level of the hot air, wherein, When the hot air is at the first utilization level, the hot air is filtered and then fed into the heating network through a heat exchanger for heating of the plant area. When the hot air is in the second utilization level, the hot air is filtered and then sent to the drying kiln to dry the ceramic tiles; When the hot air is at the third utilization level, the hot air is filtered and then sent to the firing zone for combustion support.

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