First, the application of domestic flame detector application FORNEY's flame detector is used to detect the "critical flame" of the furnace. The so-called "critical flame" means that the flame detector of a certain percentage of burners has flashed once per unit time, and it is determined that the combustion is unstable, and the MFT is extinguished. Among them, the setting of "unit time" and the selection of "a certain proportion" are based on the boiler body structure and different types of coal after a lot of tests. Flame detectors and burners are arranged in such a way that detectors form an angle between the front and rear walls and the burner, and the installation of BAILEY's flame detectors in the country is the same. 
CE's flame detector detects the "fireball" of the furnace. The entire fireball is divided into four hypothetical layers. The local installation method is to arrange the flame detectors and burners in parallel on each floor. When there are flames in two corners of each of the four corners of each layer, it is judged that there is flame in the layer; when there are less than two corners, there is no fire in the layer; if there is no fire in all the layer flame detectors, then it is determined as The furnace shuts off and MFT is performed. 
Both FORNEY and BAILEY flame detectors are good flame detectors in terms of their own performance; however, their local layout methods are significantly affected by changes in coal types for flame detection, when the coal species change At that time, the “fire point†will change, and the corresponding air distribution will change. Theoretically, the flame detector is prone to malfunction. The CE company's flame detector adopts a four-corner arrangement in parallel with the burner. It is a patent of the CE company and its detection of "fireball" is not affected by changes in coal types. According to our national conditions, coal species are subject to change. Therefore, it is more appropriate to use the company's flame detector to conduct flame monitoring on the domestic large unit furnaces. 
For the domestic CE flame detectors, in the diagnosis of fire and non-fire in the diagnostic furnace, a logic selection method of “four choices two†is adopted, that is, when any two corners in each layer are detected as fire, It is believed that there is fire in this layer; however, the flame detectors of FORNEY and BAILEY use the “four-choice three†logic selection method in the realization of logic function, that is, there are three corners in each layer with fire, and it is determined that the layer has fire. Under the condition that the unit is not under low-load combustion, even when the unit is under full-load combustion conditions, when the coal type changes, many domestic large-scale units have repeatedly caused misfires in the furnace due to misdiagnosis of detection, resulting in unnecessary MFT. Affected the safe and economic operation of the unit. Based on this, I have recommended and helped several domestic large and medium-sized power plants to modify the logic of the flame detector detection of FSSS systems, and changed the logic of layer detection from the original "four elections three" to the current "four elections." The second "to avoid the occurrence of such misjumping of these units. 
Second, ABB-CE company SAFEFLAMEI type, type II flame detector function and application SAFEFLAME flame detector is developed by the United States famous ABB-CE (formerly CE) company, has now been in dozens of countries in the power plant Wide range of applications. The SAFEFLAME flame detector has evolved from the past Type I, Type II, Type IA, Type IIB to the current DFS (Digital Flame Scanner) type, and now has more than 6,000 sets in use. SAFEFLAMEI type and II type are products developed by the United States CE company in the 1980s. There are still many applications on domestic large and medium-sized units. 
The SAFEFLAMEI and II flame detectors convert the visible light detected in the furnace into a current signal through the flame detectors at the corners of the furnace, and then input them into the electronic cabinet for processing and diagnosis. CE's Type I flame detector determines the frequency and intensity of coal powder and background fireballs in the furnace through the magnitude of the detected current. The CE type II flame detector uses the detected current to determine the frequency and intensity of the kerosene co-firing and background flames. The two are the same in the probe part of the flame detection, except that in the signal processing rack part between the electrons, there is a difference in the application of the card processing and diagnosis card. In general, there are six quick cards to achieve the display and diagnosis of fire detection, namely, strength and failure detection card, detected corner frequency detection card, detected angle strength display card, detected angle fire or no fire indicator display card, Layer "four elections two" flame diagnosis and fault alarm card, and power supply card. 
The flame detection system shall check the voltage and frequency of the supply card before selecting and putting it into use. The input voltage shall be 0.5V to 125VAC; the input frequency shall be 50HZ to 440HZ; and the output shall be before and during the normal operation of the unit. The voltage range is -15V ~ +15V (voltage output curve shown in Figure 1), flame detector output current range is -0.5A ~ +0.5A. Due to the limitation of the output current range, communication between the FSSS and the DCS system cannot be achieved normally, so that the DCS system cannot monitor the flame detection system of the model. Before the flame detection system is put into use, the initial value of the frequency and the intensity threshold of each card must be set. Generally, the frequency of coal is set at 3HZ to 5HZ, the frequency of oil is set at about 25HZ, and the intensity is set at about 20%. The specific data depends on the condition of the coal used by the factory.
The SAFEFLAMEI and Type II flame detectors are very good flame detectors for the stability of the test and the correctness of the combustion condition of the furnace in the process of putting into use for over ten years. After the normal operation, there has never been a fire due to a flame detection failure or misjudgment. Its disadvantage is that there is a limitation in controlling the output current, resulting in no full monitoring with the DCS. As a result, many power plants currently use the SAFEFLAMEDFS digital high-temperature flame detector, which is basically a replacement product developed on the SAMFIL I and II flame detectors. 
Third, the function and application of SAFEPLAMEDFS digital high temperature flame detector SAFEFLAMEDFS digital high temperature flame detector also uses the visible light band to carry out omnidirectional dynamic detection of the combustion flame, it uses a multi-fuel detection probe, a probe Simultaneous detection of different fuels such as coal, oil, and natural gas. It uses computers and large-scale integrated circuits to digitally process the flame detection signal. Compared with the original analog signal processing, the sensitivity and reliability have been further improved. The application of the flame detector digital processing makes the flame characteristic parameters digitally displayed, more clear and intuitive. Each channel of the DFS type flame detector is equipped with an independent microprocessor, which independently detects and judges the output, and has a variety of interface output methods. 
The configuration of the DFS digital high-temperature flame detector is also composed of a flame probe and a signal processing cabinet, but the cabinet and probe can be separated by up to 2000 meters. Each signal processing rack has four separate signal processing cards, a 2/4 signal, a fault output card, and a power supply card. The characteristic curve of the output voltage of the integrated circuit and the output current characteristic curve are in a logarithmic relationship. The current signal of the probe is amplified by a signal processing card, and the data is collected and A/D converted. After processing by the microprocessor, the flame signal is discriminated. The enlarged block diagram of the SAFEFLAMEDFS flame detection card is shown in FIG. 2. The DFS flame detection signal is compared with the background characteristic parameters, and is continuously judged. At the same time, a calculation is performed to obtain a comprehensive output, and characteristic parameters (frequency, intensity) are displayed.
In addition to the above functions, the DFS detector also has a flame quality parameter calculation function. The flame quality is a comprehensive reflection of the flame detection effect, which is calculated by the following formula using the current frequency, intensity, and minimum frequency and intensity value:
Quality = (I-Is) × (F-Fs) × 100 / (In × Fn) % 
Where I - current strength value
Is——minimum intensity trip value
F - current frequency value
Fs flame frequency trip value
In-——Normal Strength 〖LL〗
Fn - normal frequency value
By measuring the flame frequency, intensity and flame quality through flame detection, the flame detection equipment can be easily adjusted and set and maintained. 
The DFS digital flame detection system inputs all the feature parameters through the function keys, and the failure of the flame detection system is also displayed with an error code. Function codes F1 ~ F15, each function code represents a different meaning. The fault error code is E1~E10. In the online automatic diagnosis system, it uses its automatic fault diagnosis and scanning function ten times per second. According to the error code table of each fault, it can be easily performed when the flame fails. Diagnosis and processing bring great convenience to production and maintenance. The application range of the flame parameters of the DFS digital flame detector is shown in Table 1. 
In addition to adding the above functions, the DFS digital flame detection system has the following new features compared to Type I and Type II flame detectors: The amount of cooling air required to protect the probe is cooler than Type I and Type II cooling. The demand for wind is small, but the temperature resistance of the flame detection probe is almost doubled. The data is shown in Table 2. As can be seen from Table 2, the DFS digital flame detection system has greatly improved the environmental requirements and adaptability.
IV. Concluding remarks
As an important part of the boiler safety monitoring and protection system, the flame detector must be safe, accurate and reliable when the unit is put into production and operation. At present, China Acheng Relay Factory, Nanjing Yuguang Electric Factory and other manufacturers have developed a variety of imported and improved domestic flame detectors, and have been widely used in China's 300MW and 600MW units. Its performance and price ratio has reached the international advanced level, but in the materials, manufacturing processes and the stability of electronic components need to continue to improve and improve, as soon as possible to achieve the substitution of domestic imported equipment needs, to ensure the safe and economic operation of the unit . 
CE's flame detector detects the "fireball" of the furnace. The entire fireball is divided into four hypothetical layers. The local installation method is to arrange the flame detectors and burners in parallel on each floor. When there are flames in two corners of each of the four corners of each layer, it is judged that there is flame in the layer; when there are less than two corners, there is no fire in the layer; if there is no fire in all the layer flame detectors, then it is determined as The furnace shuts off and MFT is performed. 
Both FORNEY and BAILEY flame detectors are good flame detectors in terms of their own performance; however, their local layout methods are significantly affected by changes in coal types for flame detection, when the coal species change At that time, the “fire point†will change, and the corresponding air distribution will change. Theoretically, the flame detector is prone to malfunction. The CE company's flame detector adopts a four-corner arrangement in parallel with the burner. It is a patent of the CE company and its detection of "fireball" is not affected by changes in coal types. According to our national conditions, coal species are subject to change. Therefore, it is more appropriate to use the company's flame detector to conduct flame monitoring on the domestic large unit furnaces. 
For the domestic CE flame detectors, in the diagnosis of fire and non-fire in the diagnostic furnace, a logic selection method of “four choices two†is adopted, that is, when any two corners in each layer are detected as fire, It is believed that there is fire in this layer; however, the flame detectors of FORNEY and BAILEY use the “four-choice three†logic selection method in the realization of logic function, that is, there are three corners in each layer with fire, and it is determined that the layer has fire. Under the condition that the unit is not under low-load combustion, even when the unit is under full-load combustion conditions, when the coal type changes, many domestic large-scale units have repeatedly caused misfires in the furnace due to misdiagnosis of detection, resulting in unnecessary MFT. Affected the safe and economic operation of the unit. Based on this, I have recommended and helped several domestic large and medium-sized power plants to modify the logic of the flame detector detection of FSSS systems, and changed the logic of layer detection from the original "four elections three" to the current "four elections." The second "to avoid the occurrence of such misjumping of these units. 
Second, ABB-CE company SAFEFLAMEI type, type II flame detector function and application SAFEFLAME flame detector is developed by the United States famous ABB-CE (formerly CE) company, has now been in dozens of countries in the power plant Wide range of applications. The SAFEFLAME flame detector has evolved from the past Type I, Type II, Type IA, Type IIB to the current DFS (Digital Flame Scanner) type, and now has more than 6,000 sets in use. SAFEFLAMEI type and II type are products developed by the United States CE company in the 1980s. There are still many applications on domestic large and medium-sized units. 
The SAFEFLAMEI and II flame detectors convert the visible light detected in the furnace into a current signal through the flame detectors at the corners of the furnace, and then input them into the electronic cabinet for processing and diagnosis. CE's Type I flame detector determines the frequency and intensity of coal powder and background fireballs in the furnace through the magnitude of the detected current. The CE type II flame detector uses the detected current to determine the frequency and intensity of the kerosene co-firing and background flames. The two are the same in the probe part of the flame detection, except that in the signal processing rack part between the electrons, there is a difference in the application of the card processing and diagnosis card. In general, there are six quick cards to achieve the display and diagnosis of fire detection, namely, strength and failure detection card, detected corner frequency detection card, detected angle strength display card, detected angle fire or no fire indicator display card, Layer "four elections two" flame diagnosis and fault alarm card, and power supply card. 
The flame detection system shall check the voltage and frequency of the supply card before selecting and putting it into use. The input voltage shall be 0.5V to 125VAC; the input frequency shall be 50HZ to 440HZ; and the output shall be before and during the normal operation of the unit. The voltage range is -15V ~ +15V (voltage output curve shown in Figure 1), flame detector output current range is -0.5A ~ +0.5A. Due to the limitation of the output current range, communication between the FSSS and the DCS system cannot be achieved normally, so that the DCS system cannot monitor the flame detection system of the model. Before the flame detection system is put into use, the initial value of the frequency and the intensity threshold of each card must be set. Generally, the frequency of coal is set at 3HZ to 5HZ, the frequency of oil is set at about 25HZ, and the intensity is set at about 20%. The specific data depends on the condition of the coal used by the factory.
Third, the function and application of SAFEPLAMEDFS digital high temperature flame detector SAFEFLAMEDFS digital high temperature flame detector also uses the visible light band to carry out omnidirectional dynamic detection of the combustion flame, it uses a multi-fuel detection probe, a probe Simultaneous detection of different fuels such as coal, oil, and natural gas. It uses computers and large-scale integrated circuits to digitally process the flame detection signal. Compared with the original analog signal processing, the sensitivity and reliability have been further improved. The application of the flame detector digital processing makes the flame characteristic parameters digitally displayed, more clear and intuitive. Each channel of the DFS type flame detector is equipped with an independent microprocessor, which independently detects and judges the output, and has a variety of interface output methods. 
The configuration of the DFS digital high-temperature flame detector is also composed of a flame probe and a signal processing cabinet, but the cabinet and probe can be separated by up to 2000 meters. Each signal processing rack has four separate signal processing cards, a 2/4 signal, a fault output card, and a power supply card. The characteristic curve of the output voltage of the integrated circuit and the output current characteristic curve are in a logarithmic relationship. The current signal of the probe is amplified by a signal processing card, and the data is collected and A/D converted. After processing by the microprocessor, the flame signal is discriminated. The enlarged block diagram of the SAFEFLAMEDFS flame detection card is shown in FIG. 2. The DFS flame detection signal is compared with the background characteristic parameters, and is continuously judged. At the same time, a calculation is performed to obtain a comprehensive output, and characteristic parameters (frequency, intensity) are displayed.
In addition to the above functions, the DFS detector also has a flame quality parameter calculation function. The flame quality is a comprehensive reflection of the flame detection effect, which is calculated by the following formula using the current frequency, intensity, and minimum frequency and intensity value:
Quality = (I-Is) × (F-Fs) × 100 / (In × Fn) % 
Where I - current strength value
Is——minimum intensity trip value
F - current frequency value
Fs flame frequency trip value
In-——Normal Strength 〖LL〗
Fn - normal frequency value
By measuring the flame frequency, intensity and flame quality through flame detection, the flame detection equipment can be easily adjusted and set and maintained. 
The DFS digital flame detection system inputs all the feature parameters through the function keys, and the failure of the flame detection system is also displayed with an error code. Function codes F1 ~ F15, each function code represents a different meaning. The fault error code is E1~E10. In the online automatic diagnosis system, it uses its automatic fault diagnosis and scanning function ten times per second. According to the error code table of each fault, it can be easily performed when the flame fails. Diagnosis and processing bring great convenience to production and maintenance. The application range of the flame parameters of the DFS digital flame detector is shown in Table 1. 
In addition to adding the above functions, the DFS digital flame detection system has the following new features compared to Type I and Type II flame detectors: The amount of cooling air required to protect the probe is cooler than Type I and Type II cooling. The demand for wind is small, but the temperature resistance of the flame detection probe is almost doubled. The data is shown in Table 2. As can be seen from Table 2, the DFS digital flame detection system has greatly improved the environmental requirements and adaptability.
IV. Concluding remarks
As an important part of the boiler safety monitoring and protection system, the flame detector must be safe, accurate and reliable when the unit is put into production and operation. At present, China Acheng Relay Factory, Nanjing Yuguang Electric Factory and other manufacturers have developed a variety of imported and improved domestic flame detectors, and have been widely used in China's 300MW and 600MW units. Its performance and price ratio has reached the international advanced level, but in the materials, manufacturing processes and the stability of electronic components need to continue to improve and improve, as soon as possible to achieve the substitution of domestic imported equipment needs, to ensure the safe and economic operation of the unit . 
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