System and method for overtemperature control on platen superheater of supercritical boiler

Abstract

The invention discloses a system and a method for overtemperature control on a platen superheater of a supercritical boiler. The system comprises wall temperature sensors installed on the pipe wall of the platen superheater, an in-situ measurement device for receiving the signals of the wall temperature sensors, a power station decentralized control system DCS in communication connection with the in-situ measurement device, a first-stage monitoring loop and a second-stage monitoring loop which are connected with the in-situ measurement device and used for monitoring the wall temperature sensors, an over-fire air baffle controlled by the power station decentralized control system DCS and connected with the first-stage monitoring loop, and a desuperheating spray control valve controlled by the power station decentralized control system DCS and connected with the second-stage monitoring loop, wherein the first-stage monitoring loop comprises a first-stage speed-limiting module, a first-stage amplitude-limiting module, a first-stage OR operation module and a first-stage output pulse module; and the second-stage monitoring loop comprises a second-stage speed-limiting module, a second-stage amplitude-limiting module, a second-stage OR operation module and a second-stage output pulse module. The invention further discloses a control method of the system. The system and the method have important significance for improving the running reliability of a thermal power plant, prolonging the life of key equipment and lowering the maintenance and repair costs.

Description

technical field [0001] The invention relates to the technical field of automatic control of thermal power plants, in particular to a supercritical boiler panel superheater overtemperature control system and method. Background technique [0002] Since the 1990s, my country has successively introduced a number of supercritical units from the United States, Russia, and Japan, and gradually became the main body of my country’s high-power thermal power units. By the end of 2011, my country had become the country with the most ultra-supercritical thermal power units. It marks that my country's power industry has entered the "ultra-supercritical era". However, due to the high steam-water parameters of ultra-(ultra)critical units, they are closer to the allowable limit of materials, so it is very easy to cause unstable combustion of boilers or imbalance of dynamic heat flow in unsteady processes such as rapid changes in working conditions, resulting in high-temperature heating The o...

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Problems solved by technology

However, due to the high steam-water parameters of ultra-(ultra)critical units, they are closer to the allowable limit of materials, so it is very easy to cause unstable combustion of boilers or imbalance of dynamic heat flow in unsteady processes such as rapid changes in working conditions, resulting in high-temperature heating The overheating of the heating surface has caused a large number of serious accidents and problems such as tube explosion on the heating surface of boilers, which has a major impact on the safety and stability of power production and has become a major problem plaguing the power generation industry:

[0003] First of all, the temperature and pressure of the working fluid in the panel superheater of the supercritical boiler are very high, and it is arranged in the area with the highest flue temperature at the furnace outlet. The temperature of the tube wall on the heating surface approaches the limit service temperature of the metal material. It is very easy to cause the overheating of the metal tube wall due to system disturbance or changes in working conditions, threatening the safety of the equipment.

[0004] Second, although the outlet steam temperature of the panel superheater is maintained at the rated level by steam temperature adjustment and cross-mixing under normal operating conditions, due to the uneven distribution of the furnace smoke temperature and the flow in the heating surface tube, especially in During the dynamic process, there are deviations in the internal and external parameters of the local heating surface, which can easily cause local overheating of the heating surface under certain conditions, and even cause accelerated oxidation and tube explosion.

[0006] Fourth, as domestic power plants pay more attention to supercritical boiler wall temperature overheating, a large number of wall temperature monitoring and measuring points are generally added. Some units have installed thousands of wall temperature measuring points, but basically only can realize overtemperature Alarm after the event, it is impossible to achieve effective analysis and real-time processing of such a large number of wall temperature measurement points, to achieve over-temperature early warning and prevention, and there is no effective automatic control method available

But the current problem is that there are so many wall temperature measurement points, it is difficult to rely on manual effective analysis and monitoring, only the alarm after over-temperature can be achieved, it is difficult to realize the prediction and early warning of over-temperature, and it is still impossible to effectively use a large number of wall temperature measurement points. points to achieve effective mitigation and prevention of wall temperature overheating

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