SCR (Selective Catalytic Reduction) denitration reaction treatment method and equipment for galvanizing line flue gas

Abstract

The invention relates to the technical field of gas separation, in particular to an SCR (Selective Catalytic Reduction) denitration reaction treatment method and equipment for galvanizing line flue gas. The method comprises the following steps: collecting flue gas flow, dust concentration, flue gas temperature, catalyst temperature and nitrogen oxide concentration; constructing an activity recovery necessity index, a denitration efficiency index and a waste heat utilization potential index; the real-time heat exchange efficiency is calculated, and the power of the heating device at the collection moment is adjusted for the first time; whether the power of the heating device continues to be adjusted is judged, and if yes, the power of the heating device at the collection moment is adjusted for the second time; and the power of the heating device is repeatedly adjusted until the super-cooling starting stage is started. According to the invention, the heating power can be adaptively set, and the energy consumption of the SCR denitration reaction is reduced.

Description

Technical Field

[0001] This application relates to the field of gas separation technology, specifically to a method and equipment for SCR denitrification reaction treatment of flue gas from a galvanizing line. Background Technology

[0002] A galvanizing line, or zinc plating production line, generates high-temperature flue gas during the galvanizing process. SCR (Selective Catalytic Reduction) denitrification technology, at its core, utilizes a reducing agent, under the action of a catalyst, to selectively reduce nitrogen oxides in the flue gas, converting them into harmless nitrogen and water. SCR denitrification treatment of flue gas from galvanizing lines can effectively remove nitrogen oxides and reduce the risk of secondary pollution.

[0003] The SCR denitrification reaction method requires the reaction temperature to be kept stable between 200℃ and 400℃. However, the temperature of the flue gas from the galvanizing line flues flues significantly. When the temperature of the flue gas from the galvanizing line flues is too low, it will lead to insufficient catalyst activity and reduce the overall denitrification efficiency. Directly heating the flue gas at low temperatures will not allow for adaptive heating control based on the heat of the flue gas after denitrification, which may result in heat loss from the flue gas after denitrification and further increase energy consumption. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a method and equipment for SCR denitrification reaction treatment of flue gas from a galvanizing line, the specific technical solution of which is as follows: In one aspect, one embodiment of this application provides a method for SCR denitrification reaction treatment of flue gas from a galvanizing line, the method comprising the following steps: During the cold start-up phase of the SCR denitrification reaction of the galvanizing line flue gas, the flue gas flow rate, dust concentration, flue gas temperature, catalyst temperature and nitrogen oxide concentration at different locations were obtained at each sampling time. Based on the catalyst temperature at different collection times and locations, the necessity of activity recovery at each collection time is constructed. Combined with nitrogen oxide concentration and dust concentration, the denitrification efficiency and waste heat utilization potential index at the collection time are obtained. Analyze the flue gas temperature and dust concentration at different collection times and locations, calculate the real-time heat exchange efficiency at each collection time, and combine the waste heat utilization potential index at the collection time, as well as the differences in catalyst temperature at all locations at the collection time, the differences in flue gas flow rate and flue gas temperature at different collection times, to make the first adjustment to the power of the heating device at the collection time. Determine whether to continue adjusting the power of the heating device based on the denitrification efficiency at the time of data collection. If so, adjust the power of the heating device a second time based on the differences in denitrification efficiency within the preset time before the data collection time, the changing trend of the waste heat utilization potential index, the differences in catalyst temperature at all locations at the time of data collection, and the real-time heat exchange efficiency. Repeat the adjustment of the heating device power according to the second adjustment method until the cold start stage is passed.

[0005] Furthermore, the method for constructing the necessity of activity restoration is as follows: The catalyst activity corresponding to each catalyst temperature is obtained. The product of the normalized value of the mean catalyst temperature at the same location during the cold start phase and the catalyst activity of the mean catalyst temperature is recorded as the relative catalyst activity at the last sampling time corresponding to all catalyst temperatures at that location. The mean of the relative catalyst activities at all catalyst locations at the same sampling time is recorded as the average activity index of the catalyst at the same sampling time. The necessity for activity recovery is positively correlated with the average activity index and negatively correlated with the catalyst activity corresponding to the catalyst temperature.

[0006] Furthermore, the method for obtaining the denitrification efficiency is as follows: The ratio of the difference between the nitrogen oxide concentrations at the inlet and outlet of the SCR reactor at the sampling time to the nitrogen oxide concentration at the inlet is recorded as the denitrification efficiency at the sampling time.

[0007] Furthermore, the method for obtaining the waste heat utilization potential index is as follows: The normalized value of the ratio of the necessity for activity recovery to the denitrification efficiency at the time of sampling is denoted as the usable waste heat index of the denitrified flue gas at the time of sampling. The waste heat utilization potential index is negatively correlated with the waste heat availability index of the denitrified flue gas and positively correlated with the dust concentration.

[0008] Furthermore, the method for calculating the real-time heat exchange efficiency at the time of data acquisition is as follows: The difference between the average flue gas temperature at the SCR reactor outlet and the heat exchanger outlet at the sampling time and all sampling times before the sampling time during the denitrification reaction process is used as the numerator, and the difference between the average flue gas temperature at the SCR reactor outlet and the preheating device outlet at the sampling time and all sampling times before the sampling time during the denitrification reaction process is used as the denominator. The value of the fraction is recorded as the real-time heat exchange efficiency of the heat exchanger at the sampling time. The real-time heat exchange efficiency is positively correlated with the difference in dust concentration, and the real-time heat exchange efficiency is negatively correlated with the dust concentration.

[0009] Furthermore, the method for the first adjustment of the heating device power at the time of data acquisition is as follows: The uniformity of catalyst activity at the time of sampling is determined by the difference in catalyst temperature at all locations at the sampling time. The flow rate stability at different sampling times was determined based on the flue gas flow rate at different sampling times. The temperature stability at different sampling times was determined based on the differences in flue gas temperature at different sampling times. The control coefficients at the time of data acquisition are calculated. These control coefficients are positively correlated with real-time heat exchange efficiency, catalyst activity uniformity, and flow stability, and negatively correlated with temperature stability. The difference between the outlet flue gas temperature of the preheating device and the original flue gas temperature at the time of data collection is recorded as the flue gas preheating demand temperature difference at the time of data collection. The ratio of the waste heat utilization potential index to the flue gas preheating demand temperature difference at the time of data collection is recorded as the waste heat satisfaction ratio at the time of data collection. Based on the control coefficient, waste heat satisfaction ratio, control coefficient, and heating device power at the time of data collection, the heating device power is adjusted for the first time.

[0010] Furthermore, the first adjustment of the heating device power based on the control coefficient, waste heat satisfaction ratio, control coefficient, and heating device power at the time of data acquisition includes the following specific steps: The product of the difference between the number 1 and the product of the control coefficient and the residual heat satisfaction ratio at the time of data acquisition, and the power of the heating device at the time of data acquisition, is recorded as the adjusted heating power at the time of data acquisition. The maximum value of the adjusted heating power at the time of data acquisition and the value of the number 0 are taken as the first adjustment value of the heating device power at the time of data acquisition.

[0011] Furthermore, the specific steps for determining whether to continue adjusting the power of the heating device based on the denitrification efficiency at the time of data collection are as follows: When the denitrification efficiency at the time of data collection is greater than the preset second efficiency threshold, the power of the heating device is not adjusted; otherwise, the power of the heating device is adjusted.

[0012] Furthermore, the method for adjusting the power of the heating device at the time of data acquisition a second time is as follows: Based on the difference in denitrification efficiency between adjacent collection times within a preset time period before the collection time, the normalized efficiency change rate at the collection time is determined. Based on the changing trend of the waste heat utilization potential index within a preset time period before the data collection time, the slope of the fitted line corresponding to the data collection time is obtained. The weighted sum of the normalized efficiency change rate and the slope of the fitted line at the acquisition time is recorded as the first coefficient at the acquisition time. The positive correlation between the first coefficient at the acquisition time, the catalyst activity uniformity, and the real-time heat exchange efficiency is recorded as the comprehensive correction coefficient at the acquisition time. The product of the difference between the number 1 and the comprehensive correction coefficient at the acquisition time and the primary adjustment power of the heating device at the acquisition time is used as the value of the second adjustment of the heating device power at the acquisition time.

[0013] Secondly, another embodiment of this application provides an SCR denitrification reaction treatment device for flue gas from a galvanizing line, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the aforementioned SCR denitrification reaction treatment method for flue gas from a galvanizing line.

[0014] The embodiments of this application have at least the following beneficial effects: During the cold start-up phase of SCR denitrification, since the denitrification reaction is exothermic, a potential analysis of waste heat utilization is conducted to avoid wasting flue gas waste heat during the SCR denitrification cold start-up phase. The waste heat utilization potential index is obtained at the time of data collection. In the process of using the waste heat of denitrated flue gas to preheat the non-denitrated flue gas, the operating condition of the heat exchanger directly determines the waste heat preheating effect. Therefore, based on the real-time heat exchange efficiency of the heat exchanger, combined with the temperature and flow stability of the denitrated flue gas, the preheating effect corresponding to the current waste heat utilization potential index is determined, and the power of the heating device at the time of data collection is dynamically adjusted for the first time based on the waste heat preheating effect. Furthermore, considering that in the SCR denitrification process, the denitrated flue gas... When preheating the untreated flue gas with waste heat, changes in the preheating heat source may cause abnormal fluctuations in denitrification efficiency. Therefore, it is necessary to continue to monitor the trend of denitrification efficiency in real time, make a second adjustment to the power of the heating device at the time of data collection, and repeat the adjustment process in the same way. When the denitrification efficiency is abnormal, the heating device is used to supplement heat in a timely manner to ensure the denitrification efficiency until the cold start stage is passed. During the entire cold start stage, the galvanizing line flue gas is heated adaptively according to the temperature and heat of the denitrified flue gas to solve the problem of excessive energy consumption in the SCR denitrification reaction caused by unreasonable heating power settings, which leads to heat loss of the denitrified flue gas or insufficient catalyst activity. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the steps of an SCR denitrification reaction treatment method for flue gas from a galvanizing line, as provided in one embodiment of this application. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of an SCR denitrification reaction treatment method and equipment for galvanized line flue gas proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] The following, in conjunction with the accompanying drawings, details the specific scheme of the SCR denitrification reaction treatment method and equipment for galvanizing line flue gas provided in this application.

[0020] Please see Figure 1 The diagram illustrates a flowchart of an SCR denitrification reaction treatment method for flue gas from a galvanizing line according to an embodiment of this application. The method includes the following steps: Step S001: During the cold start-up phase of the SCR denitrification reaction of the galvanizing line flue gas, acquire the flue gas flow rate, dust concentration, flue gas temperature, catalyst temperature, and nitrogen oxide concentration at different locations at each sampling time.

[0021] Before performing SCR denitrification treatment on the flue gas from the galvanizing line, it is necessary to complete the directional collection of flue gas, impurity filtration, and data acquisition.

[0022] The core objective of directional flue gas collection is to ensure flue gas convergence efficiency and reduce temperature loss. The specific steps are as follows: 1. Collecting dispersed flue gas: The dispersed flue gas generated by the direct combustion section and the radiant section of the galvanizing line is collected through a pre-set dedicated exhaust flue. The direct combustion section is the fuel combustion heating zone, and the radiant section is the high-temperature radiant heat exchange zone.

[0023] 2. Dynamic adjustment of the flow: An electric regulating damper valve is installed at the branch inlet of the exhaust flue. The valve opening is dynamically adjusted according to the real-time emission of the two sections of flue gas to ensure that the flue gas is evenly distributed into the main pipe and to avoid uneven temperature caused by local eddies. The branch inlet of the exhaust flue is where the flue gas from the direct combustion section and the radiation section enters the main pipe.

[0024] 3. Stabilize airflow: An airflow stabilization section is set at the end of the main exhaust duct, and the built-in guide plate guides the flue gas to flow smoothly, improving the stability of subsequent filtration processes.

[0025] The flue gas impurity filtration process involves removing impurities and particulate matter from the collected flue gas using physical filtration methods. Specific equipment includes filter screens and baghouse desulfurization dust collectors. The filter screens intercept larger dust particles in the flue gas, while the baghouse desulfurization dust collectors remove fine dust particles smaller than 0.1 micrometers.

[0026] Among them, flue gas data acquisition and storage means that during the flue gas gathering and filtration process, data is acquired in real time by installing multiple types of sensors at key locations on the equipment.

[0027] The sensor and the collected data are as follows: 1. Temperature sensor A: Installed at the end of the main exhaust gas duct, the outlet of the bag filter desulfurizer dust collector, the inlet and outlet of the SCR reactor, the outlet of the heat exchanger, and the outlet of the preheating device, respectively, to collect the original flue gas temperature, the pretreated flue gas temperature, the flue gas temperature at the inlet and outlet of the SCR reactor, the flue gas temperature at the outlet of the heat exchanger, and the flue gas temperature at the outlet of the preheating device.

[0028] 2. Temperature sensor B: Distributedly installed in the catalyst bed, used to collect the temperature of multiple points in the catalyst bed within the SCR reactor, and to obtain the catalyst temperature at different locations within the SCR reactor.

[0029] 3. Flue gas flow sensor: Installed before the steady flow section of the main flue gas duct, it is used to collect flue gas flow rate, which is the total amount of flue gas emitted between adjacent collection times.

[0030] 4. Dust concentration sensor: installed at the outlet of the bag filter desulfurization dust collector to collect dust concentration.

[0031] 5. Nitrogen oxide concentration sensor: Installed at the inlet and outlet of the SCR reactor respectively, the nitrogen oxide concentration is used to monitor the denitrification effect.

[0032] All sensors are uniformly set to a data acquisition frequency of 1 time per minute. After real-time preprocessing, the acquired data is stored in a designated area of ​​the equipment system to construct an SCR denitrification reaction processing database.

[0033] Thus, the flue gas flow rate, dust concentration, flue gas temperature, catalyst temperature, and nitrogen oxide concentration at different locations were obtained at each sampling time.

[0034] Step S002: Based on the catalyst temperature at different collection times and locations, construct the necessity for activity recovery at each collection time, and obtain the waste heat utilization potential index at each collection time by combining nitrogen oxide concentration and dust concentration.

[0035] During the cold start-up phase of the SCR denitrification reaction, the equipment needs to directly preheat the flue gas generated by the galvanizing line using a heating device to ensure that the flue gas temperature meets the process requirements of the denitrification reaction. It is worth noting that the denitrification reaction is exothermic; after the reaction, the flue gas usually maintains a relatively high temperature, generally not lower than the preheated flue gas temperature. To avoid wasting flue gas waste heat, a potential analysis of waste heat utilization during the SCR denitrification cold start-up phase is necessary to determine the potential for utilizing waste heat that can be used for preheating the non-denitrified flue gas.

[0036] During the cold start phase, the catalyst activity recovers as the temperature rises. Based on the catalyst temperature at all locations from the start of the cold start phase to the sampling time, the catalyst activity at the sampling time is evaluated, and the average activity index of the catalyst at the sampling time is obtained.

[0037] Preferably, as an embodiment of this application, the catalyst activity corresponding to each catalyst temperature is obtained based on the catalyst activity curve of the catalyst with temperature change provided by the catalyst manufacturer. The normalized value of the average catalyst temperature at the same position during the cold start stage is multiplied by the catalyst activity of the average catalyst temperature, and recorded as the catalyst relative activity at the last sampling time corresponding to all catalyst temperatures at that position. The average of the catalyst relative activities at all catalyst positions at the same sampling time is recorded as the average activity index of the catalyst at the same sampling time.

[0038] The normalized value of the mean catalyst temperature is the ratio of the mean catalyst temperature to the maximum catalyst temperature.

[0039] The average activity index is the level of activity that a catalyst should achieve at the time of collection.

[0040] The necessity of activity recovery at the time of data collection is determined by comparing the average activity index at the time of data collection with the catalyst activity corresponding to the catalyst temperature. The necessity of activity recovery is positively correlated with the average activity index, and negatively correlated with the catalyst activity corresponding to the catalyst temperature.

[0041] It is understood that the positive and negative correlations in this application refer to the relationship between the independent and dependent variables. A positive correlation means that the dependent variable increases (decreases) as the independent variable increases (decreases), and can be an additive or multiplicative relationship. A negative correlation means that the dependent variable decreases (increases) as the independent variable increases (decreases), and can be an inverse relationship or a subtractive relationship.

[0042] Preferably, as an embodiment of this application, the normalized value of the difference between the average activity index at the sampling time and the catalyst activity corresponding to the catalyst temperature is recorded as the activity recovery necessity at the sampling time.

[0043] The normalized value of the difference between the average activity index at the time of collection and the catalyst activity corresponding to the catalyst temperature is greater than or equal to -1 and less than or equal to 1. In this embodiment, a linear normalization algorithm is used to achieve normalization.

[0044] The greater the need for activity recovery at the time of collection, the more the catalyst activity at the time of collection is lower than the expected activity. In this case, it is more necessary to prioritize preheating temperature to restore activity, that is, the stronger the need to prioritize using heating devices to increase flue gas temperature.

[0045] The denitrification efficiency at the time of sampling is calculated based on the difference in nitrogen oxide concentration at the inlet and outlet.

[0046] The ratio of the difference between the nitrogen oxide concentrations at the inlet and outlet of the SCR reactor at the sampling time to the nitrogen oxide concentration at the inlet is recorded as the denitrification efficiency at the sampling time.

[0047] When the denitrification efficiency at the time of sampling is greater than or equal to the preset first efficiency threshold, the denitrification efficiency is determined to be up to standard, and the residual heat of the denitrified flue gas is used to preheat the non-denitrified flue gas; when the denitrification efficiency at the time of sampling is less than the preset first efficiency threshold, the denitrification efficiency is determined to be down to standard, and the flue gas temperature at the inlet of the SCR reactor must be guaranteed first, and the heating device must be used to preheat the flue gas first.

[0048] In this embodiment, the first efficiency threshold is set to 0.9.

[0049] The normalized value of the ratio of the necessity for activity recovery to the denitrification efficiency at the time of collection is denoted as the denitrified flue gas waste heat availability index at the time of collection. Based on the denitrified flue gas waste heat availability index and the dust concentration at the time of collection, the waste heat utilization potential index at the time of collection is calculated. The waste heat utilization potential index is negatively correlated with the denitrified flue gas waste heat availability index, and the waste heat utilization potential index is positively correlated with the dust concentration.

[0050] In the process of calculating the ratio, in order to avoid the denominator being zero, a preset value needs to be added to the denominator. In this example, the preset value is 0.0001.

[0051] The ratio of the usable waste heat of the denitrified flue gas at the time of collection to the dust concentration is recorded as the first ratio at the time of collection. The product of the difference between the number 1 and the first ratio at the time of collection and the waste heat of the reaction at the time of collection is recorded as the waste heat utilization potential index at the time of collection.

[0052] In calculating the waste heat utilization potential index, the dimension of dust concentration is: Dust concentration is calculated by substituting numerical values, without substituting dimensions. In the process of calculating ratios, to avoid the denominator being zero, a preset value needs to be added to the denominator. In this example, the preset value is 1. The residual heat of the reaction at the time of collection is obtained through the heat calculation formula. The residual heat of the reaction at the time of collection is the heat of the flue gas at the time of collection. The heat of the flue gas at the time of collection is the product of the specific heat capacity, mass, and temperature change of the flue gas. The heat calculation formula is a well-known technique and will not be elaborated further.

[0053] While considering the catalytic and denitrification efficiency during the cold start phase, the waste heat utilization potential is comprehensively evaluated to obtain a waste heat utilization potential index. The higher the temperature and the lower the dust concentration, the greater the waste heat utilization potential and the higher the waste heat utilization potential index.

[0054] Thus, the waste heat utilization potential index at the time of collection is obtained.

[0055] Step S003: Analyze the flue gas temperature and dust concentration at different collection times and locations, calculate the real-time heat exchange efficiency at each collection time, and combine the waste heat utilization potential index at the collection time, as well as the differences in catalyst temperature at all locations at the collection time, the differences in flue gas flow rate and flue gas temperature at different collection times, to make the first adjustment to the power of the heating device at the collection time.

[0056] In the process of preheating non-denitrified flue gas using the waste heat of denitrified flue gas, the heat exchanger plays a crucial role, and its operating conditions directly determine the preheating effect. By considering the temperature and flow stability of the denitrified flue gas, the operating stability of the heat exchanger can be further refined. Specifically, the smaller the temperature and flow fluctuations and the higher the stability of the flue gas, the higher the heat transfer efficiency of the heat exchange process. Based on this, the preheating effect corresponding to the current waste heat utilization potential index can be determined, and the goal of dynamically adjusting the operating parameters of the heating device based on the waste heat preheating effect can be achieved, i.e., the initial adjustment of the heating device power at the time of data collection.

[0057] Based on the flue gas temperature and dust concentration at different collection times and locations, the real-time heat exchange efficiency at each collection time is calculated.

[0058] The difference between the average flue gas temperature at the SCR reactor outlet and the heat exchanger outlet at the sampling time and all previous sampling times during the denitrification reaction process is used as the numerator. The difference between the average flue gas temperature at the SCR reactor outlet and the preheating device outlet at the sampling time and all previous sampling times during the denitrification reaction process is used as the denominator. The value of the fraction is recorded as the real-time heat exchange efficiency of the heat exchanger at the sampling time. Based on the dust concentration and the real-time heat exchange efficiency of the heat exchanger at the sampling time, the real-time heat exchange efficiency at the sampling time is calculated. The real-time heat exchange efficiency is positively correlated with the difference in dust concentration, and negatively correlated with the dust concentration.

[0059] Preferably, as an embodiment of this application, the product of the difference between the number 1 and the dust concentration at the time of collection and the real-time heat exchange efficiency of the heat exchanger is recorded as the real-time heat exchange efficiency at the time of collection.

[0060] In calculating the real-time heat exchange efficiency, the dimension of dust concentration is: Dust concentration is calculated by substituting numerical values, without substituting dimensions into the calculation process.

[0061] The mean value of the catalyst temperature at all locations at the sampling time is recorded as the average catalyst temperature at the sampling time. The ratio of the standard deviation of the catalyst temperature at all locations at the sampling time to the average catalyst temperature at the sampling time is recorded as the relative difference of the catalyst temperature at the sampling time. The difference between the number 1 and the relative difference of the catalyst temperature at the sampling time is recorded as the uniformity of catalyst activity at the sampling time.

[0062] It should be noted that during the cold start-up phase of SCR denitrification, the load on the galvanizing line fluctuates significantly, which can easily lead to noticeable fluctuations in the flow rate of the denitrified flue gas. Directly adjusting the preheating device parameters based on the instantaneous flue gas flow rate would cause frequent start-ups and shutdowns of the heating device, greatly increasing system energy consumption. Therefore, it is necessary to analyze the flow stability of the denitrified flue gas.

[0063] The average flue gas flow rate at the time of collection is the mean of the flue gas flow rate between all adjacent collection times within a preset time period before the collection time. The ratio of the standard deviation of the flue gas flow rate between all adjacent collection times within a preset time period before the collection time to the average flue gas flow rate at the collection time is recorded as the relative difference of the flue gas flow rate at the collection time. The difference between the number 1 and the relative difference of the flue gas flow rate at the collection time is recorded as the flow stability at the collection time.

[0064] The average flue gas temperature at the time of collection is the mean of all adjacent collection times within a preset time period before the collection time. The ratio of the standard deviation of the flue gas temperature at all adjacent collection times within a preset time period before the collection time to the average flue gas temperature at the time of collection is the relative difference of flue gas temperature at the time of collection. The difference between the number 1 and the relative difference of flue gas temperature at the time of collection is the temperature stability at the time of collection.

[0065] In this embodiment, the preset duration is set to 5 minutes.

[0066] Based on the real-time heat exchange efficiency, catalyst activity uniformity, flow rate stability, and temperature stability at the time of data acquisition, control coefficients are calculated. These control coefficients are positively correlated with the real-time heat exchange efficiency, catalyst activity uniformity, and flow rate stability, respectively, and negatively correlated with the temperature stability.

[0067] Preferably, as an embodiment of this application, the normalized value of the ratio of the product of real-time heat exchange efficiency, catalyst activity uniformity and flow stability at the time of data acquisition to temperature stability is recorded as the control coefficient at the time of data acquisition.

[0068] In the process of calculating the ratio, to avoid the denominator being zero, a preset value needs to be added to the denominator. In this embodiment, the preset value is 1. The control coefficient is greater than or equal to -1 and less than or equal to 1. In this embodiment, a linear normalization algorithm is used to achieve normalization.

[0069] The difference between the preheating device outlet flue gas temperature and the original flue gas temperature at the time of data collection is recorded as the flue gas preheating demand temperature difference at the time of data collection. The ratio of the waste heat utilization potential index to the flue gas preheating demand temperature difference at the time of data collection is recorded as the waste heat satisfaction ratio at the time of data collection. The difference between the number 1 and the product of the control coefficient and the control coefficient at the time of data collection is calculated. The product of the difference of the product and the power of the heating device at the time of data collection is recorded as the adjusted heating power at the time of data collection. The maximum value of the adjusted heating power and the number 0 at the time of data collection is recorded as the primary heating device adjusted power at the time of data collection.

[0070] In the process of calculating and adjusting the heating power, the dimension of the waste heat utilization potential index is joules, and the dimension of the flue gas preheating demand temperature difference is degrees Celsius. The waste heat utilization potential index and the flue gas preheating demand temperature difference are only substituted into the calculation with numerical values, and the dimensions are not substituted into the calculation process.

[0071] The higher the residual heat satisfaction ratio at the time of data collection, the better the residual heat can satisfy the reaction, and the more necessary it is to reduce the power of the heating device. The difference in the product results in the adjustment range of the heating device power at the time of data collection; the larger the difference in the product, the greater the adjustment range of the heating device power at the time of data collection.

[0072] It should be noted that, under the premise of meeting the denitrification efficiency, waste heat should be used to preheat the flue gas that has not been denitrified.

[0073] The power of the heating device at the time of data acquisition is used as the power value of the heating device at the time of data acquisition, thereby realizing the first adjustment of the power of the heating device.

[0074] This completes the first adjustment of the heating device's power.

[0075] Step S004: Determine whether to continue adjusting the power of the heating device based on the denitrification efficiency at the time of data collection. If so, adjust the power of the heating device at the time of data collection a second time based on the differences in denitrification efficiency within the preset time before the data collection time, the changing trend of the waste heat utilization potential index, the differences in catalyst temperature at all locations at the time of data collection, and the real-time heat exchange efficiency. Repeat the adjustment of the power of the heating device according to the second adjustment method until the cold start stage is passed.

[0076] In the SCR denitrification process, when using the waste heat from denitrified flue gas to preheat unnitrified flue gas, the change in the preheating heat source may lead to abnormal fluctuations in denitrification efficiency. Therefore, in the initial stage of waste heat preheating operation, it is necessary to continue to monitor the trend of denitrification efficiency in real time. When the denitrification efficiency becomes abnormal, the heating device should be used to supplement the heat in a timely manner to ensure the denitrification efficiency.

[0077] After the first adjustment of the heating device power, if the denitrification efficiency at the sampling time is greater than the preset second efficiency threshold, it is determined that the sampling time is in an optimal balance state, and no further adjustment of the heating device power is made. If the denitrification efficiency at the sampling time is less than or equal to the preset second efficiency threshold, it is determined that the sampling time is not in an optimal balance state, and further adjustment of the heating device power is required. The preset second efficiency threshold should be greater than the first efficiency threshold; in this embodiment, the second efficiency threshold is set to 0.95.

[0078] The steps for further adjusting the power of the heating device are as follows.

[0079] The average of the differences in denitrification efficiency between adjacent collection times within a preset time period before the collection time is recorded as the short-term trend of denitrification efficiency at the collection time. The difference between the preset second efficiency threshold and the first efficiency threshold is used as the denominator, and the short-term trend of denitrification efficiency at the collection time is used as the numerator. The normalized value of the fraction is recorded as the normalized efficiency change rate at the collection time.

[0080] When the short-term trend of the denitrification efficiency at the time of sampling is greater than 0, the denitrification efficiency generally shows an upward trend within the preset time before the sampling time, which means that the first adjustment of the heating device power is adapted to the utilization of waste heat; when the short-term trend of the denitrification efficiency at the time of sampling is less than or equal to 0, the denitrification efficiency generally shows a downward trend or a stable trend within the preset time before the sampling time, which means that the first adjustment of the heating device power does not meet the needs of waste heat utilization.

[0081] Based on the waste heat utilization potential index at the time of collection and all previous collection times, the time of collection is used as the independent variable and the waste heat utilization potential index is used as the dependent variable. A linear fit is performed on the time of collection and the waste heat utilization potential index to obtain the slope of the fitted line corresponding to the time of collection.

[0082] In this embodiment, the least squares method is used to achieve linear fitting.

[0083] The weighted sum of the normalized efficiency change rate and the slope of the fitted line at the acquisition time is recorded as the first coefficient at the acquisition time. The positive correlation between the first coefficient at the acquisition time, the catalyst activity uniformity, and the real-time heat exchange efficiency is recorded as the comprehensive correction coefficient at the acquisition time. The product of the difference between the number 1 and the comprehensive correction coefficient at the acquisition time and the primary heating device adjustment power at the acquisition time is recorded as the secondary heating device adjustment power at the acquisition time.

[0084] Preferably, as an embodiment of this application, when weighted summing the normalized efficiency change rate at the acquisition time and the slope of the fitted line, the weights of the normalized efficiency change rate at the acquisition time and the slope of the fitted line are 0.6 and 0.4, respectively; the product of the first coefficient at the acquisition time, the uniformity of catalyst activity, and the real-time heat exchange efficiency is recorded as the comprehensive correction coefficient at the acquisition time.

[0085] It is understandable that the comprehensive correction coefficient at the time of data collection is greater than or equal to -1 and less than or equal to 1. When the comprehensive correction coefficient at the time of data collection is greater than 0, the power of the heating device at the time of data collection needs to be reduced, that is, the denitrification efficiency at the time of data collection increases and the residual heat is sufficient. When the comprehensive correction coefficient at the time of data collection is less than 0, the power of the heating device at the time of data collection needs to be increased, that is, the denitrification efficiency at the time of data collection decreases and the residual heat is insufficient.

[0086] The power of the secondary heating device at the time of data acquisition is used as the power value of the heating device at the time of data acquisition, thereby realizing the second adjustment of the power of the heating device.

[0087] Following the method of adjusting the power of the heating device a second time, the power of the heating device is adjusted repeatedly until the transition conditions of the cold start stage are met, thus determining that the cold start stage of the SCR denitrification reaction treatment has been successfully completed.

[0088] The cold start transition conditions are as follows: the inlet flue gas temperature of the SCR reactor remains greater than or equal to 200℃ and less than or equal to 220℃ for 5 consecutive minutes; simultaneously, the denitrification efficiency at all sampling moments for 5 consecutive minutes is greater than a preset third efficiency threshold. The third efficiency threshold should be greater than the first efficiency threshold; in this embodiment, the third efficiency threshold is set to 0.9.

[0089] Thus, the temperature coordination control of the heating device for the SCR denitrification reaction of the galvanizing line flue gas is realized.

[0090] This application also proposes an SCR denitrification reaction treatment device for flue gas from a galvanizing line, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it performs the steps described above. Since a method for SCR denitrification reaction treatment of flue gas from a galvanizing line has been described in detail above, it will not be repeated here.

[0091] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments of this specification have been described above. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0092] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0093] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for treating flue gas from a galvanizing line using SCR denitrification reaction, characterized in that, The method includes the following steps: During the cold start-up phase of the SCR denitrification reaction of the galvanizing line flue gas, the flue gas flow rate, dust concentration, flue gas temperature, catalyst temperature and nitrogen oxide concentration at different locations were obtained at each sampling time. Based on the catalyst temperature at different collection times and locations, the necessity of activity recovery at each collection time is constructed. Combined with nitrogen oxide concentration and dust concentration, the denitrification efficiency and waste heat utilization potential index at the collection time are obtained. Analyze the flue gas temperature and dust concentration at different collection times and locations, calculate the real-time heat exchange efficiency at each collection time, and combine the waste heat utilization potential index at the collection time, as well as the differences in catalyst temperature at all locations at the collection time, the differences in flue gas flow rate and flue gas temperature at different collection times, to make the first adjustment to the power of the heating device at the collection time. Determine whether to continue adjusting the power of the heating device based on the denitrification efficiency at the time of data collection. If so, adjust the power of the heating device a second time based on the differences in denitrification efficiency within the preset time before the data collection time, the changing trend of the waste heat utilization potential index, the differences in catalyst temperature at all locations at the time of data collection, and the real-time heat exchange efficiency. Repeat the adjustment of the heating device power according to the second adjustment method until the cold start stage is passed.

2. The SCR denitrification reaction treatment method for flue gas from a galvanizing line according to claim 1, characterized in that, The method for constructing the necessity of activity restoration is as follows: The catalyst activity corresponding to each catalyst temperature is obtained. The product of the normalized value of the mean catalyst temperature at the same location during the cold start phase and the catalyst activity of the mean catalyst temperature is recorded as the relative catalyst activity at the last sampling time corresponding to all catalyst temperatures at that location. The mean of the relative catalyst activities at all catalyst locations at the same sampling time is recorded as the average activity index of the catalyst at the same sampling time. The necessity for activity recovery is positively correlated with the average activity index and negatively correlated with the catalyst activity corresponding to the catalyst temperature.

3. The SCR denitrification reaction treatment method for flue gas from a galvanizing line according to claim 1, characterized in that, The method for obtaining the denitrification efficiency is as follows: The ratio of the difference between the nitrogen oxide concentrations at the inlet and outlet of the SCR reactor at the sampling time to the nitrogen oxide concentration at the inlet is recorded as the denitrification efficiency at the sampling time.

4. The SCR denitrification reaction treatment method for flue gas from a galvanizing line according to claim 1, characterized in that, The method for obtaining the waste heat utilization potential index is as follows: The normalized value of the ratio of the necessity for activity recovery to the denitrification efficiency at the time of sampling is denoted as the usable waste heat index of the denitrified flue gas at the time of sampling. The waste heat utilization potential index is negatively correlated with the waste heat availability index of the denitrified flue gas and positively correlated with the dust concentration.

5. The SCR denitrification reaction treatment method for flue gas from a galvanizing line according to claim 1, characterized in that, The method for calculating the real-time heat exchange efficiency at the time of data acquisition is as follows: The difference between the average flue gas temperature at the SCR reactor outlet and the heat exchanger outlet at the sampling time and all sampling times before the sampling time during the denitrification reaction process is used as the numerator, and the difference between the average flue gas temperature at the SCR reactor outlet and the preheating device outlet at the sampling time and all sampling times before the sampling time during the denitrification reaction process is used as the denominator. The value of the fraction is recorded as the real-time heat exchange efficiency of the heat exchanger at the sampling time. The real-time heat exchange efficiency is positively correlated with the difference in dust concentration, and the real-time heat exchange efficiency is negatively correlated with the dust concentration.

6. The SCR denitrification reaction treatment method for galvanizing line flue gas according to claim 1, characterized in that, The method for the first adjustment of the heating device power at the time of data acquisition is as follows: The uniformity of catalyst activity at the time of sampling is determined by the difference in catalyst temperature at all locations at the sampling time. The flow rate stability at different sampling times was determined based on the flue gas flow rate at different sampling times. The temperature stability at different sampling times was determined based on the differences in flue gas temperature at different sampling times. The control coefficients at the time of data acquisition are calculated. These control coefficients are positively correlated with real-time heat exchange efficiency, catalyst activity uniformity, and flow stability, and negatively correlated with temperature stability. The difference between the outlet flue gas temperature of the preheating device and the original flue gas temperature at the time of data collection is recorded as the flue gas preheating demand temperature difference at the time of data collection. The ratio of the waste heat utilization potential index to the flue gas preheating demand temperature difference at the time of data collection is recorded as the waste heat satisfaction ratio at the time of data collection. Based on the control coefficient, waste heat satisfaction ratio, control coefficient, and heating device power at the time of data collection, the heating device power is adjusted for the first time.

7. The SCR denitrification reaction treatment method for flue gas from a galvanizing line according to claim 6, characterized in that, The first adjustment of the heating device power based on the control coefficient, waste heat satisfaction ratio, control coefficient, and heating device power at the time of data acquisition includes the following specific steps: The product of the difference between the number 1 and the product of the control coefficient and the residual heat satisfaction ratio at the time of data acquisition, and the power of the heating device at the time of data acquisition, is recorded as the adjusted heating power at the time of data acquisition. The maximum value of the adjusted heating power at the time of data acquisition and the value of the number 0 are taken as the first adjustment value of the heating device power at the time of data acquisition.

8. The SCR denitrification reaction treatment method for galvanizing line flue gas according to claim 1, characterized in that, The specific steps for determining whether to continue adjusting the power of the heating device based on the denitrification efficiency at the time of data collection are as follows: When the denitrification efficiency at the time of data collection is greater than the preset second efficiency threshold, the power of the heating device is not adjusted; otherwise, the power of the heating device is adjusted.

9. The SCR denitrification reaction treatment method for flue gas from a galvanizing line according to claim 1, characterized in that, The method for adjusting the power of the heating device at the time of data acquisition a second time is as follows: Based on the difference in denitrification efficiency between adjacent collection times within a preset time period before the collection time, the normalized efficiency change rate at the collection time is determined. Based on the changing trend of the waste heat utilization potential index within a preset time period before the data collection time, the slope of the fitted line corresponding to the data collection time is obtained. The weighted sum of the normalized efficiency change rate and the slope of the fitted line at the acquisition time is recorded as the first coefficient at the acquisition time. The positive correlation between the first coefficient at the acquisition time, the catalyst activity uniformity, and the real-time heat exchange efficiency is recorded as the comprehensive correction coefficient at the acquisition time. The product of the difference between the number 1 and the comprehensive correction coefficient at the acquisition time and the primary adjustment power of the heating device at the acquisition time is used as the value of the second adjustment of the heating device power at the acquisition time.

10. An SCR denitrification reaction treatment device for flue gas from a galvanizing line, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the SCR denitrification reaction treatment method for galvanized line flue gas as described in any one of claims 1 to 9.

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