Method for determining optimal temperature window position of biomass vibrating grate boiler SNCR

Abstract

The application discloses a method for determining the optimal temperature window position of a biomass vibrating grate boiler SNCR. The method comprises the following steps: collecting the dynamic data of the flue gas temperature at different height positions in the furnace; collecting the dynamic data of the flue gas temperature at different positions in the horizontal section of the furnace; and determining the dynamic position of the temperature window of the full load and full furnace by the established dynamic characteristic parameters of the flue gas temperature. The dynamic position of the SNCR temperature window is determined by continuously monitoring and dynamically analyzing the flue gas temperature at different positions of the full load and full furnace through the established dynamic characteristic parameters of the SNCR temperature window flue gas temperature.

Description

Technical fields:

[0001] This invention relates to a method for dynamically determining the SNCR temperature window position in a biomass boiler. Background technology:

[0002] Biomass energy is the energy that organisms obtain through photosynthesis, convert solar energy into chemical energy, and store in biomass. It originates from the photosynthesis of plants, and the carbon dioxide produced by its combustion is basically equal to the carbon dioxide absorbed, thus achieving zero carbon emissions.

[0003] Biomass boilers use biomass energy as fuel. Among them, the biomass direct combustion power generation technology using vibrating grate high-temperature and high-pressure boilers is a mature and advanced technology that has been practiced abroad for many years and has been listed by the United Nations as a global promotion project. The vibrating grate is a grate that periodically adds fuel and discharges ash by vibrating, which is very suitable for burning biomass fuel. However, precisely because of the grate vibration, the combustion, NOx generation and flue gas temperature in the furnace also exhibit periodic fluctuations.

[0004] SNCR (Synchronous Non-Catalytic Reduction) denitrification technology is the preferred choice for controlling NOx emissions from biomass boilers. This technology, without the aid of a catalyst, uses an atomized injection system to inject a reducing agent (10%–40% urea solution or 10%–25% ammonia water) into the furnace, reducing nitrogen oxides in the flue gas into harmless nitrogen and water. This technology can reduce ammonia leakage and escape under suitable temperature conditions to ensure ideal denitrification efficiency; the suitable temperature range for the SNCR denitrification reaction is called the "temperature window."

[0005] When the reaction temperature is below the lower limit of the temperature window, the reaction time is much longer than the residence time of the flue gas in the furnace, the denitrification reaction rate decreases, and the denitrification efficiency shows a linear decreasing trend. As the reaction temperature increases, the denitrification reaction rate increases, and the denitrification efficiency increases linearly. However, when the temperature rises to a high level, NH3 is oxidized to NOx, and the denitrification efficiency decreases linearly. Figure 1 As shown.

[0006] Since the advent of SNCR denitrification technology, numerous researchers both domestically and internationally have conducted detailed studies on its reaction mechanism, experimental characteristics, and influencing factors. Studies generally agree that the main factors affecting SNCR denitrification efficiency include: reaction temperature, reaction time, ammonia-to-nitrogen molar ratio, and reductant injection location. Among these, depending on the reductant and SNCR operating conditions, the optimal temperature window for the SNCR denitrification reaction typically occurs between 850 and 1100℃. If the temperature is too high or too low, both the reductant utilization rate and the denitrification efficiency will decrease.

[0007] In practical engineering applications, the furnace temperature changes with various factors such as boiler load, fuel source, and heat exchange efficiency of the furnace and heating surfaces. Consequently, the optimal temperature window for the denitrification reaction also shifts. However, the injection position of the reducing agent remains fixed, making it challenging to maintain a high denitrification efficiency over the long term. [6] .

[0008] For vibrating grate boilers, the aforementioned problems become more complex due to the periodic vibration of the grate. This is because the flue gas temperature and NOx formation within the furnace exhibit additional periodic fluctuations on a minute-by-minute basis, and the optimal temperature window for the denitrification reaction also changes dynamically. Furthermore, the poor uniformity of the existing reducing agent mixing with the flue gas significantly impacts the denitrification efficiency of this type of boiler, ultimately requiring a simple increase in the ammonia-to-nitrogen molar ratio (increasing the amount of reducing agent) to meet national flue gas emission standards.

[0009] Currently, biomass vibrating grate boilers that meet ultra-low emission standards generally suffer from a series of problems, such as high urea consumption, significant ammonia escape in flue gas, ammonium bisulfate sedimentation, increased boiler flue gas resistance, and limited boiler load.

[0010] Therefore, for the SNCR denitrification system widely used in biomass vibrating grate boilers, in order to maximize the overlap between the reductant injection position and the optimal temperature window position, and to ensure that the injection position meets the requirement of uniform mixing of the reductant and flue gas as much as possible, it is necessary to construct a test method for the dynamic position of the optimal temperature window. This will provide reliable data for SNCR ammonia injection modification and operation adjustment, and has very important practical significance. Summary of the Invention

[0011] To overcome the above-mentioned defects, the purpose of this invention is to provide a method for determining the dynamic position of the SNCR temperature window in a biomass vibrating grate boiler.

[0012] To achieve the above objectives, the present invention provides a method for dynamically determining the SNCR temperature window position in a biomass vibrating grate boiler, the method comprising at least the following steps:

[0013] (1) Collect dynamic data of flue gas temperature at predetermined heights inside the furnace;

[0014] (2) Collect dynamic data of flue gas temperature at different positions of the horizontal cross section at predetermined heights inside the furnace;

[0015] (3) The dynamic position of the temperature window under full load and full furnace is determined by establishing the dynamic characteristic parameters of flue gas temperature.

[0016] Furthermore, the method specifically includes:

[0017] (1) Under typical load, dynamic data of flue gas temperature at different heights in the furnace are continuously collected through dynamic monitoring of flue gas temperature throughout the furnace.

[0018] (2) Under typical load, dynamic data of flue gas temperature at different locations on the horizontal cross section of the furnace are continuously collected through dynamic monitoring of flue gas temperature across the entire cross section.

[0019] (3) By establishing the dynamic characteristic parameters of flue gas temperature, the dynamic position of the temperature window at full load (50% to 100% of rated load) and the entire furnace is determined.

[0020] Furthermore, the dynamic characteristic parameters of the smoke temperature include: relative smoke temperature L of the temperature window and the overlap degree of the smoke temperature O of the temperature window. t The calculation formula and judgment criteria are as follows:

[0021] L=(t a -T l ) / (T h -T l )×100, Unit: %

[0022] t a The average flue gas temperature at a specific location on the boiler, measured in °C.

[0023] T l The lower limit of the SNCR temperature window is set at 850℃.

[0024] T h The upper limit of the SNCR temperature window is set to 1100℃;

[0025] When t a <T l When L is less than 0%, the average flue gas temperature is below the lower limit of the temperature window and is not within the temperature window;

[0026] When t a >T h When L is greater than 100%, the average flue gas temperature is higher than the upper limit of the temperature window and is not within the temperature window;

[0027] When T l <t a <T h When L is between 0% and 100%, and the average flue gas temperature is within the temperature window, the boiler location is considered a practically selectable location for the SNCR temperature window.

[0028] O t =n t / N×100, unit: %

[0029] When T l <t i <T h n t =n t +1, n t The initial value is 0;

[0030] t i The i-th (0 < i ≤ N) horizontal section flue gas temperature (average of multiple flue gas temperatures within the section) at a certain height position of the boiler during the test period, °C;

[0031] N is the total number of points of continuously monitored flue gas temperature data at a certain position of the boiler at equal time intervals during the test period, number;

[0032] n t The number of points of continuously monitored flue gas temperature data within the SNCR temperature window, number;

[0033] When O t > 80%, it is considered that this boiler position can be used as the actual optional position of the SNCR temperature window.

[0034] Furthermore, the above-mentioned flue gas temperature dynamic characteristic parameters also include: over-temperature redundancy θ, the calculation formula and determination condition are:

[0035] θ = T am - t a , unit: °C

[0036] T am is the flue gas temperature over-temperature alarm value, T am = T hh - δ a / 2, unit °C;

[0037] T hh is the over-temperature limit value of the denitrification reaction, T hh = T h + 50, when T hh > 1200 °C, T hh = 1200, unit °C, too high flue gas temperature will cause a large amount of NH3 to be oxidized to NO X . In the high-temperature (above 1200 °C) region, the rate of the oxidation reaction increases faster with the increase of temperature [7] . Therefore, the above over-temperature limit value of the reaction should be at least less than 1200 °C.

[0038] When θ > 0 °C, it is considered that this boiler position can be used as the actual optional position of the SNCR temperature window.

[0039] Furthermore, the above-mentioned flue gas temperature dynamic characteristic parameters also include: the mean value of the maximum flue gas temperature deviation of the section δ a The calculation formula is:

[0040] δ a = average(δ1, δ2, δ3, δ4, δ i ……), unit: °C

[0041] δi represents the maximum smoke temperature deviation at a certain height at the i-th time point monitored at consecutive equal time intervals. The number of measuring points arranged on this cross-section should not be less than 4. For a horizontal test cross-section with multiple test points, the maximum smoke temperature deviation (maximum smoke temperature - minimum smoke temperature) of the smoke temperature values ​​measured at these measuring points at the same time node is δi. This is used to understand the non-uniformity of the smoke temperature at the same height position on the horizontal cross-section and to avoid excessively high smoke temperatures in local areas leading to oxidation of the reducing agent.

[0042] Furthermore, by using dynamic monitoring data parameters and data of flue gas temperature throughout the furnace, it can be determined whether each location can be used as a practically selectable location for the SNCR temperature window;

[0043] Among them, the whole furnace flue gas temperature test dynamically monitors the flue gas temperature at no less than 2, 1 and 2 height positions in the three areas of the boiler furnace, throat and combustion chamber, respectively, in order to analyze the dynamic changes and characteristic parameters of the flue gas temperature at each position and determine whether each position can be used as a practically selectable position for the SNCR temperature window.

[0044] When 0% <ta<100%、O t When >80% and θ>0, the boiler is considered to be in a practically selectable position within the SNCR temperature window, and the SNCR reaction window position is preliminarily determined.

[0045] Furthermore, by using full-load flue gas temperature dynamic monitoring data, we can confirm whether each location can be used as a practically selectable location for the SNCR temperature window;

[0046] Among them, the full-load flue gas temperature test should be conducted within the range of 50% to 100% of the rated load, with at least two loads, high and low. One load should be used for dynamic monitoring of the flue gas temperature throughout the furnace, and the other load should be used for verification testing to understand the changes in the dynamic characteristic parameters of flue gas temperature at key locations under different loads.

[0047] This invention establishes dynamic characteristic parameters of flue gas temperature within the SNCR temperature window, continuously monitors and dynamically analyzes the flue gas temperature at different locations throughout the furnace under full load, and determines the dynamic position of the SNCR temperature window. Attached Figure Description

[0048] Figure 1 Effect of reaction temperature on SNCR denitrification efficiency

[0049] Figure 2 Continuous monitoring curve of smoke temperature

[0050] Figure 3 Continuous monitoring curve of maximum flue gas temperature deviation at a certain horizontal section inside the furnace

[0051] Figure 4Dynamic flue gas temperature characteristics at various locations within a typical load furnace; where (a) is the dynamic flue gas temperature fluctuation curve in the upper part of the furnace region; (b) is the dynamic flue gas temperature fluctuation curve in the middle part of the furnace region; (c) is the dynamic flue gas temperature fluctuation curve in the lower part of the furnace region; (d) is the dynamic flue gas temperature fluctuation curve in the throat region; (e) is the dynamic flue gas temperature fluctuation curve in the upper part of the combustion chamber region; (not consistent with the figure) (f) is the dynamic flue gas temperature fluctuation curve in the lower part of the combustion chamber region.

[0052] Figure 5 Dynamic characteristic curves of multi-point flue gas temperature in the lower part of the furnace under typical load

[0053] Figure 6 Dynamic characteristic curve of maximum deviation of flue gas temperature at the lower section of the furnace under typical load

[0054] Figure 7 Schematic diagram of test setup and measurement point locations Detailed Implementation

[0055] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0056] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0057] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0058] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] Example:

[0060] The boiler in a certain biomass power plant is a 135t / h biomass grate boiler that adopts advanced foreign biofuel combustion technology. The boiler is a high-temperature, high-pressure parameter natural circulation boiler, with a single drum, single furnace, balanced ventilation, indoor layout, solid ash discharge, all-steel frame, and bottom support structure.

[0061] Because the existing fuel deviates from the design fuel, it uses crop straw with high moisture content (>25%), low calorific value, and high density, resulting in a low combustion temperature inside the furnace. The furnace area (the main area where SNCR is currently located) shows a DCS flue gas temperature of only 700-900℃, near the lower limit of the optimal SNCR reaction temperature window (850-1100℃). The overlap between the SNCR unit's reaction temperature range and the optimal temperature window is very limited. Therefore, since the unit was put into operation, due to the incomplete utilization of SNCR denitrification effect, urea consumption is very high, and ammonia escape from the tail flue is significant, resulting in great environmental and operational pressures.

[0062] Based on the fundamental principles of combustion and relevant flue gas temperature data, it is known that the flue gas temperature in the boiler throat and combustion chamber region is relatively high, resulting in a greater overlap with the optimal temperature window. However, because the flue gas temperature in this region dynamically changes with the grate vibration cycle, the specific location of the denitrification reaction temperature window also dynamically changes accordingly. To achieve the best denitrification effect of SNCR, it is necessary to determine the dynamic location of the optimal SNCR temperature window for this biomass vibrating grate boiler in order to facilitate subsequent related modifications.

[0063] 1) Dynamic monitoring of flue gas temperature throughout the furnace (typical load)

[0064] Under typical load, continuous dynamic flue gas temperature monitoring was conducted at three height positions (3, 1, and 2) in three zones of the biomass boiler furnace: furnace, throat, and combustion chamber. The dynamic characteristic curves of the flue gas temperature at these six different positions are shown below. Figure 4 As shown.

[0065] Depend on Figure 4 It can be known that:

[0066] Under typical load, the flue gas temperature in the furnace, which is the main area for SNCR, flue gas temperature fluctuations are relatively small, but the overall flue gas temperature is too low (the average flue gas temperature in both the upper and lower parts of the furnace is lower than the lower limit of the temperature window), resulting in a significant reduction in SNCR denitrification performance. 2) Dynamic monitoring of flue gas temperature across the entire cross-section (typical load)

[0067] Under typical load, continuous dynamic flue gas temperature monitoring was conducted simultaneously at four locations in the main SNCR (lower part of the furnace) area of ​​the biomass boiler to understand the maximum flue gas temperature fluctuation at each location across the entire cross-section. The dynamic characteristic curves of the flue gas temperature at the four different locations are shown below. Figure 5 , Figure 6 As shown.

[0068] Depend on Figure 5 , Figure 6 It can be seen that:

[0069] Under typical load, at the lower part of the furnace area which is the main layout position of SNCR, the maximum flue gas temperature difference in the horizontal section at the same time at this position is 92 - 217 °C, and the time-averaged value is 157 °C. That is, the flue gas temperature deviation at different positions of this section is about 157 °C, and from this, it can be known that the flue gas temperature alarm value is 1072 °C.

[0070] 3) Analysis and judgment of the dynamic position of the full-furnace temperature window (typical load)

[0071] Under typical load (50% of the rated load), based on the full-furnace flue gas temperature test data at the above 6 height positions, the dynamic characteristic parameters of the flue gas temperature at each position are calculated and summarized, as shown in Table 1.

[0072] Table 1 Summary of the dynamic characteristic parameter data of the flue gas temperature at different height positions in the full-furnace area (50% of the rated load)

[0073]

[0074] The order and process for determining whether each position can be an actual optional position for the SNCR temperature window are as follows:

[0075] (1) Judgment basis through the dynamic characteristic parameter of flue gas temperature "relative position of the flue gas temperature window": When 0% < ta < 100%, it is considered to meet the requirements.

[0076] From this judgment, at the middle of the furnace area, the throat area, the upper part of the combustion chamber area, and the lower part of the combustion chamber area under typical load meet the requirements, but the relative positions of the flue gas temperature windows are 12%, 14%, 22%, and 18% respectively (average 15%), and the overall is near the lower limit temperature of the flue gas window. It can be seen that the overall flue gas temperature level in the boiler furnace under typical load (50% of the rated load) is relatively low.

[0077] (2) Judgment basis through the dynamic characteristic parameter of flue gas temperature "coincidence rate of the flue gas temperature in the temperature window": When Ot > 80%, it is considered to meet the requirements.

[0078] From this judgment, at the middle of the furnace area, the throat area, the upper part of the combustion chamber area, and the lower part of the combustion chamber area under typical load meet the requirements, and the coincidence rates of the flue gas temperature are 90%, 60%, 90%, and 80% respectively. That is, the time when the flue gas temperature maintains within the flue gas temperature window range at the above positions accounts for a relatively high proportion, and the part exceeding the flue gas temperature window range is in the low-temperature category, and there is no long-term high flue gas temperature state.

[0079] Judgment basis through the dynamic characteristic parameter of flue gas temperature "over-temperature redundancy": When θ > 0, it is considered to meet the requirements.

[0080] Therefore, it was determined that the average flue gas temperature in all test areas of the boiler under typical load did not exceed Tam (1072℃), indicating that there was no overheating phenomenon in the denitrification reaction inside the boiler.

[0081] In summary, under typical loads, the dynamic characteristics of flue gas temperature at four locations—the central part of the furnace region, the throat region, the upper part of the combustion chamber region, and the lower part of the combustion chamber region—all meet the requirements. The area within the furnace region that meets the requirements is relatively small; therefore, it is preliminarily considered that the SNCR reaction window should be located in the throat and combustion chamber regions. Furthermore, the average flue gas temperature in the throat and combustion chamber regions ranges from 885 to 904℃, with a fluctuation of approximately 20℃, indicating relatively uniform overall flue gas temperature in this spatial region.

[0082] 4) Analysis and judgment of the dynamic position of the temperature window in the entire furnace (100% rated load)

[0083] Under 100% rated load, the dynamic characteristic parameters of flue gas temperature at each location in the lower part and throat area of ​​the furnace were calculated, summarized and verified based on the flue gas temperature test data of the entire furnace, as shown in Table 2.

[0084] Table 2 Summary of dynamic flue gas temperature parameters at different heights throughout the furnace (100% rated load)

[0085]

[0086] The order and process for confirming whether each location can be used as an actual selectable location for the SNCR temperature window are as follows:

[0087] The following can be determined by analyzing the dynamic characteristic parameters of flue gas temperature: "relative position of flue gas temperature window", "overlap rate of flue gas temperature window", and "over-temperature alarm limit".

[0088] (1) Compared with 50% rated load, the maximum fluctuation of flue gas temperature in the lower part of the furnace area at 100% rated load has decreased, but the overall flue gas temperature has not increased at all, and still cannot meet the requirements of the parameters of "relative position of flue gas temperature window" and "overlap rate of flue gas temperature window".

[0089] Therefore, it can be seen that the range of the furnace area that meets the relatively required dynamic characteristics of flue gas temperature under full load is relatively small, and it is not suitable as the actual arrangement area of ​​the SNCR temperature window.

[0090] (2) Compared with 50% rated load, the maximum fluctuation of flue gas temperature in the throat area of ​​100% rated load is reduced, and the overall flue gas temperature is increased from 885℃ to 936℃, an increase of about 50℃. Although the increase is not large, the "relative position of flue gas temperature window" and "overlap rate of flue gas temperature window" are significantly improved, and there is still a redundancy of 136℃ with the over-temperature alarm value (1072℃).

[0091] At 50% rated load, the flue gas temperature in the combustion chamber area is slightly higher than that in the throat area (about 20°C higher). Even considering the high fluctuation range of flue gas temperature in the burner area, the burner area at 100% rated load will still meet the requirements of the relevant dynamic flue gas temperature characteristics under the high redundancy of 136°C.

[0092] It can be seen that the throat and combustion chamber regions meet the requirements of flue gas temperature dynamic characteristic parameters under full load. Since the two regions are connected, the denitrification reaction range is large, making them suitable as the actual arrangement area for the SNCR temperature window.

[0093] 5) Determination of the temperature window position for the denitrification reaction

[0094] By continuously monitoring and dynamically analyzing the flue gas temperature at different locations throughout the furnace under full load, the optimal location of the SNCR temperature window is determined, taking into account the following factors:

[0095] (1) Under full load (50% to 100%), the flue gas temperature in the furnace, which is the main area for SNCR, is too low. The area that meets the relevant parameter requirements is small, and the SNCR denitrification performance is significantly reduced. It is no longer suitable as the SNCR reaction window location.

[0096] (2) Under full load (50% to 100%), the throat and combustion chamber regions both meet the requirements of flue gas temperature dynamic characteristic parameters. Since the two regions are connected, the denitrification reaction range is large, making it suitable as the actual arrangement area for the SNCR temperature window.

[0097] (3) Due to changes in fuel, coking in the furnace and failure to adjust operating parameters according to design requirements, the overall temperature inside the existing boiler has dropped significantly, and the original denitrification reaction temperature window has shifted significantly from the furnace area to the combustion chamber area.

[0098] (4) Currently, the boiler also has the problem of "NO in the furnace". X The system suffers from numerous problems, such as "poor uniformity of concentration" and "inability to install ammonia injection devices in certain areas." Therefore, it is necessary to extend the denitrification reaction time and improve the mixing uniformity of flue gas and ammonia to enhance denitrification efficiency. The advantages of designating the combustion chamber and throat areas as the actual layout areas for the SNCR temperature window are as follows:

[0099] 1) The overall flue gas temperature in the combustion chamber is high, which can significantly improve the SNCR denitrification reaction rate;

[0100] 2) The combustion chamber is located at the bottom of the boiler, which advances the mixing time of urea and flue gas, which not only helps to increase the denitrification reaction time, but also improves the mixing effect;

[0101] 3) The airflow disturbance in the combustion chamber is significant, which undoubtedly improves the mixing effect of urea and flue gas.

[0102] The present invention has been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described above. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Many other changes and modifications made without departing from the concept and scope of the present invention should be considered within the scope of protection of the present invention.

[0103] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0104] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for determining the optimal temperature window position for non-suspension temperature recirculation (SNCR) in a biomass vibrating grate boiler, characterized in that, The method described in detail is as follows: Under typical load, dynamic data of flue gas temperature at different heights inside the furnace are continuously collected through dynamic monitoring of flue gas temperature throughout the furnace. Under typical load, dynamic flue gas temperature data at different locations on the horizontal cross-section at various heights inside the furnace are continuously collected through full-section dynamic monitoring. By establishing dynamic flue gas temperature characteristic parameters, the dynamic position of the temperature window under full load and full furnace is determined; The dynamic characteristics of the smoke temperature include: relative smoke temperature L within the temperature window and the overlap degree of smoke temperature within the temperature window O. t The calculation formula and judgment criteria are as follows: L = (t) a -T l ) / (T h -T l ) × 100, unit: % t a The average flue gas temperature at a certain height position of the boiler during continuous monitoring of the horizontal cross-section, in °C; T l The lower limit of the SNCR temperature window is set at 850℃. T h The upper limit of the SNCR temperature window is set to 1100℃; When t a <T l When L is less than 0%, the average flue gas temperature is below the lower limit of the temperature window and is not within the temperature window; When t a >T h When L is greater than 100%, the average flue gas temperature is higher than the upper limit of the temperature window and is not within the temperature window; When T l <t a < T h When L is between 0% and 100%, and the average flue gas temperature is within the temperature window, the boiler location is considered as the actual selectable location for the SNCR temperature window. O t = n t / N×100, unit: % When T l < t i <T h n t = n t + 1, n t The initial value is 0; t i Let be the flue gas temperature at the i-th horizontal cross-section continuously monitored at equal time intervals at a certain height position of the boiler during the test, ℃; where 0 <i≤N; N represents the total number of data points (number of points) used to continuously monitor flue gas temperature at a specific location on the boiler at equal time intervals during the test. n t The number of points within the SNCR temperature window for continuous, equally timed monitoring of smoke temperature data; When O t When the accuracy rate is >80%, the boiler location is considered as a practically selectable location for the SNCR temperature window; The aforementioned dynamic characteristic parameters of flue gas temperature also include: overtemperature redundancy θ, the calculation formula and judgment condition are as follows: θ = T am -t a Unit: ℃ T am T is the alarm value for smoke temperature exceeding the limit. am =T hh -δ a / 2, in °C; T hh For the denitrification reaction exceeding the temperature limit, T hh =T h +50; When θ>0℃, the boiler location is considered as the actual selectable location for the SNCR temperature window.

2. The method for determining the optimal SNCR temperature window position in a biomass vibrating grate boiler according to claim 1, characterized in that, The aforementioned dynamic characteristic parameters of smoke temperature also include: the average value δ when the cross-section has the maximum smoke temperature deviation. a The calculation formula is: d a = average ( δ1, δ2, δ3, δ4, δ i …… ) , unit:℃ δi represents the maximum smoke temperature deviation at a certain height at the i-th time point monitored at continuous equal time intervals. The number of measuring points arranged at this cross-section should not be less than 4.

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