CN-122016143-A - Ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method and device

CN122016143ACN 122016143 ACN122016143 ACN 122016143ACN-122016143-A

Abstract

The invention belongs to the technical field of online monitoring of flue gas treatment, and relates to a method and a device for dynamic monitoring and grading early warning of resistance of an SCR inlet flue. The method is characterized by comprising the steps of measuring the total section flow by adopting an ultrasonic multichannel time difference method, setting static pressure measuring points on a flow field stable section, calculating equivalent resistance characterization quantity as a core monitoring parameter based on measured flue pressure drop delta P and flue gas volume flow Q to eliminate the influence of flow change, constructing and online updating a dynamic base line R base based on a historical R value sequence in a sliding time window, and finally, realizing graded early warning by calculating the relative deviation between a current R value and the dynamic base line, namely an abnormal index epsilon and a change rate g. The invention effectively solves the technical problems of insufficient representativeness, easy blocking drift and false alarm and missing report of fixed threshold value of the traditional method due to the traditional differential pressure monitoring, remarkably improves the accuracy and reliability of early warning, and provides technical support for realizing predictive maintenance of the SCR system.

Inventors

WU YUEJIAN
FAN SHIJIE
WANG CHENGLIANG
LIU KAI
ZHAO HONGTAO
GUO HAIYING
TI HUI
GAO GUOQING
LIU SONGSONG
LI CHAOQUN

Assignees

华电淄博热电有限公司
华电国际电力股份有限公司技术服务分公司
西安格瑞电力科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260324

Claims (10)

1. The ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method is characterized by comprising the following steps of: S1, selecting a measurement interval in a straight section of an SCR inlet flue, and setting an upstream static pressure measuring point and a downstream static pressure measuring point in the measurement interval to obtain an upstream static pressure P up and a downstream static pressure P down by measurement, wherein the selection of the measurement interval meets the condition of stable flow field; s2, measuring an ultrasonic measurement section in the measurement interval by adopting an ultrasonic multichannel time difference method to obtain the volume flow Q of the flue gas flowing through the measurement interval; S3, determining the pressure drop delta P between measuring points based on the difference value of the upstream static pressure P up and the downstream static pressure P down ; s4, calculating an equivalent resistance characterization quantity R=delta P/Q2 at the current moment based on the pressure drop delta P and the volume flow Q; S5, calculating a dynamic baseline R base and carrying out online updating based on a historical data sequence of the equivalent resistance characterization quantity R in a sliding time window; The sliding time window is a data interval formed by forward tracing N historical moments by taking the current moment as an end point, wherein N is a positive integer greater than 1; S6, calculating an abnormality index epsilon and a change rate g based on the equivalent resistance characterization quantity R at the current moment and the dynamic base line R base , wherein epsilon= (R-R base )/R base , ; S7, respectively comparing the abnormality index epsilon with a preset first threshold epsilon 1 and a second threshold epsilon 2 , and comparing the change rate g with a change rate threshold g th , wherein epsilon 2 >ε 1 ; s8, outputting an early warning signal according to the comparison result and the following rule; If the second early warning condition is met, outputting a second-stage early warning signal; And if the second early warning condition is not met but the first early warning condition is met, outputting a first-stage early warning signal.
2. The dynamic monitoring and early warning method for the resistance of the ultrasonic full-section SCR flue according to claim 1, wherein the ultrasonic multi-channel time difference method adopts a 4-channel structure, the 4-channel structure is composed of ultrasonic transducers arranged on opposite side walls of the flue and is divided into an upper layer and a lower layer which are arranged in a crossing manner along the height direction of the section, the upper layer two channels form a crossing X structure, the lower layer two channels form a crossing X structure, and the symmetrical multi-path measuring structure of the upper layer X and the lower layer X is formed.
3. The ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method according to claim 1, further comprising: measuring an ultrasonic measurement section in the measurement interval by adopting an ultrasonic multichannel time difference method to obtain the average speed of the smoke section ; Based on the average velocity of the flue gas section And smoke density Calculating the resistance coefficient ; Wherein the density of the flue gas The method is calculated by combining the flue gas temperature T measured in real time with the known standard state density and utilizing the simplified form of an ideal gas state equation.
4. The method for dynamically monitoring and pre-warning the resistance of the ultrasonic full-section SCR flue according to claim 1, wherein the calculating the dynamic baseline R base and the online updating based on the historical data sequence of the equivalent resistance characterization quantity R comprise: Processing a historical resistance characterization quantity R in a sliding time window based on a preset cleaning state characterization strategy to generate a baseline candidate value representing a low resistance level, wherein the cleaning state characterization strategy is low-ranking statistics or lower envelope extraction; And fusing the baseline candidate value into a historical baseline by adopting an exponential smoothing or recursive filtering algorithm, and outputting an updated dynamic baseline R base .
5. The method for dynamically monitoring and pre-warning the resistance of the ultrasonic full-section SCR flue according to claim 1, wherein the outputting the pre-warning signal according to the comparison result according to the following rule specifically comprises: And outputting a second-level early warning signal when one of the following conditions is met and a second jitter elimination condition is met at the same time: A:ε≥ε 2 ; B, epsilon is larger than or equal to epsilon 1 , and g is larger than or equal to g th ; the first-stage early warning condition is that when the second-stage early warning condition is not met but the condition epsilon is more than or equal to epsilon 1 and the first jitter eliminating condition is met, a first-stage early warning signal is output; The first jitter elimination condition is that the occurrence frequency of the abnormal state epsilon is more than or equal to epsilon 1 reaches the preset continuous frequency N 1 within a preset duration time window T 1 ; The second jitter elimination condition is that, in a preset duration window T 2 , the number of occurrence of abnormal states satisfying one of the following conditions reaches a preset continuous number N 2 : A:ε≥ε 2 ; b: epsilon is larger than or equal to epsilon 1 and g is more than or equal to g th .
6. The ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method according to claim 1 is characterized by further comprising the steps of generating and outputting a soot blowing linkage signal when a secondary early warning signal is output, wherein the linkage signal is used for controlling the starting of soot blowing equipment; wherein, output the soot blowing linkage signal needs to satisfy one or more interlocking conditions, the interlocking conditions include: a, a time interval of executing soot blowing action according to the soot blowing linkage signal is adjacent to a preset shortest soot blowing interval time; the soot blowing system is in a ready state for allowing soot blowing; c, the soot blowing action times in unit time do not reach the upper limit; d, after the abnormal index epsilon self-triggering secondary early warning, falling back to be below a release threshold epsilon 1 -delta and continuing for a set stable time Where δ is a return difference parameter greater than zero.
7. An ultrasonic full-section SCR flue resistance dynamic monitoring and early warning device is characterized by comprising: The data acquisition module is used for selecting a measurement interval at the straight section of the SCR inlet flue, and setting upstream and downstream static pressure measuring points in the measurement interval to obtain upstream static pressure P up and downstream static pressure P down in a measuring way; The ultrasonic flow measurement module is used for measuring an ultrasonic measurement section in the measurement interval by adopting an ultrasonic multichannel time difference method to obtain the volume flow Q of the flue gas flowing through the measurement interval; The first data processing module is used for determining the pressure drop delta P between measuring points based on the difference value of the upstream static pressure P up and the downstream static pressure P down ; And is further configured to calculate an equivalent resistance characterization r=Δp/Q2 at the current moment based on the pressure drop Δp and the volumetric flow Q; The resistance modeling module is used for calculating a dynamic baseline R base and carrying out online updating based on a historical data sequence of the equivalent resistance characterization quantity R in a sliding time window; The second data processing module is used for calculating an abnormality index epsilon and a change rate g based on the equivalent resistance characterization quantity R at the current moment and the dynamic baseline R base , wherein epsilon= (R-R base )/R base ; ; The third data processing module is used for comparing the abnormality index epsilon with a preset first threshold epsilon 1 and a second threshold epsilon 2 respectively and comparing the change rate g with a change rate threshold g th , wherein epsilon 2 >ε 1 ; the grading early warning judging module is used for outputting early warning signals according to the comparison result and the following rules; If the second early warning condition is met, outputting a second-stage early warning signal; And if the second early warning condition is not met but the first early warning condition is met, outputting a first-stage early warning signal.
8. The ultrasonic full-section SCR flue resistance dynamic monitoring and early warning device according to claim 6, further comprising a linkage module: The linkage module is used for triggering a soot blowing instruction when receiving the secondary alarm signal.
9. The ultrasonic full-section SCR flue resistance dynamic monitoring and early warning device of claim 6, wherein the resistance modeling module further comprises: The first resistance modeling unit is used for processing the historical resistance characterization quantity R in the sliding time window based on a preset cleaning state characterization strategy to generate a baseline candidate value representing a low resistance level; and the second resistance modeling unit is used for fusing the baseline candidate value into a historical baseline by adopting an exponential smoothing or recursive filtering algorithm and outputting an updated dynamic baseline R base .
10. The ultrasonic full-section SCR flue resistance dynamic monitoring and early warning device of claim 1, wherein the staged early warning determination module comprises: the first early warning unit is used for outputting a second-level early warning signal when one of the following conditions is met and a second jitter elimination condition is met at the same time: A:ε≥ε 2 ; B, epsilon is larger than or equal to epsilon 1 , and g is larger than or equal to g th ; The second early warning unit outputs a first early warning signal when the second early warning condition is not met but the condition epsilon is more than or equal to epsilon 1 and the first jitter elimination condition is met at the same time; a condition storage unit configured to store the first debounce condition and the second debounce condition; The first jitter elimination condition is that the occurrence frequency of the abnormal state epsilon is more than or equal to epsilon 1 reaches the preset continuous frequency N 1 within a preset duration window T 1 ; The second jitter elimination condition is that, in a preset duration window T 2 , the number of occurrence of abnormal states satisfying one of the following conditions reaches a preset continuous number N 2 : A:ε≥ε 2 ; b: epsilon is larger than or equal to epsilon 1 and g is more than or equal to g th .

Description

Ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method and device Technical Field The invention belongs to the technical field of heat energy and power engineering and on-line monitoring of flue gas treatment of coal-fired units, and relates to a dynamic monitoring and early warning method and device for ultrasonic full-section SCR flue resistance. Background With increasingly strict environmental protection requirements, an SCR (selective catalytic reduction) denitration system has become a core device for purifying flue gas of a coal-fired unit. The resistance of the SCR inlet flue is a key parameter reflecting the running state of the system, the abnormal change of the resistance not only can cause the energy consumption of the induced draft fan to increase dramatically, but also can cause tripping of the unit when serious, thereby forming a direct threat to the safe and stable running of the unit. Currently, the SCR inlet flue resistance monitoring mainly adopts a single-point differential pressure measurement technology. According to the method, the differential pressure transmitter is arranged at a specific position of the flue, and the partial differential pressure is measured to calculate the total section resistance. However, because the distribution of the flow field of the SCR inlet flue is extremely uneven and severe working conditions such as high temperature, high dust, dust accumulation and the like exist, single-point measurement data cannot truly reflect the average flow field state of the whole section, so that the resistance calculation error is large and the false alarm rate is high. In addition, the prior art has serious environmental adaptability problems. Meanwhile, the differential pressure transmitter is easy to generate signal drift in long-term operation, so that the long-term reliability of monitoring data is reduced, and the requirement of long-term online operation is difficult to meet. In addition, in the prior art, a fixed threshold is generally adopted for alarm judgment, so that the obvious influence of flow fluctuation caused by unit load change on a pressure drop signal can not be overcome, and false alarm missing are frequently generated. More importantly, the method lacks the normalized representation of resistance characteristics and dynamic baseline tracking capability, so that normal working condition fluctuation and real resistance deterioration are difficult to distinguish, and early warning and grading treatment cannot be realized. Therefore, the prior art can not realize the accurate sensing and intelligent early warning of the resistance of the SCR inlet flue under the complex environment of high-temperature high-dust and variable-working-condition operation. Disclosure of Invention The invention aims to provide an ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method and device, which are used for solving the problems of inaccurate sensing and inadvisable early warning of the SCR inlet flue resistance caused by non-representative monitoring, unreliable measurement and stiff early warning logic in the prior art. In order to achieve the purpose, the specific technical scheme of the ultrasonic full-section SCR flue resistance dynamic monitoring and early warning method provided by the invention is as follows: S1, selecting a measurement interval in a straight section of an SCR inlet flue, and setting an upstream static pressure measuring point and a downstream static pressure measuring point in the measurement interval to obtain an upstream static pressure P up and a downstream static pressure P down by measurement, wherein the selection of the measurement interval meets the condition of stable flow field; s2, measuring an ultrasonic measurement section in the measurement interval by adopting an ultrasonic multichannel time difference method to obtain the volume flow Q of the flue gas flowing through the measurement interval; S3, determining the pressure drop delta P between measuring points based on the difference value of the upstream static pressure P up and the downstream static pressure P down; s4, calculating an equivalent resistance characterization quantity R=delta P/Q2 at the current moment based on the pressure drop delta P and the volume flow Q; S5, calculating a dynamic baseline R base and carrying out online updating based on a historical data sequence of the equivalent resistance characterization quantity R in a sliding time window; The sliding time window is a data interval formed by forward tracing N historical moments by taking the current moment as an end point, wherein N is a positive integer greater than 1; S6, calculating an abnormality index epsilon and a change rate g based on the equivalent resistance characterization quantity R at the current moment and the dynamic base line R base, wherein epsilon= (R-R base)/Rbase, ; S7, respectively comparing the abnormality index epsilo