Study Of Tube Wall Temperature Monitoring On High-temperature Convection Heating Surface Of Utility Boiler

In recent years, the thermal power generation units have been developing in the trend of larger capacity and higher parameter. The structural design and arrangement of the superheater and reheater get complicated increasingly, which inevitably aggravate the hydrodynamic and thermal load deviation in the parallel tube set systems. It leads to the overheating and tube rupture on high-temperature convection heating surface of utility boiler, seriously decreasing the security and economy of the thermal power systems. Consequently, it is significant in engineering to study a computation model to calculate the tube wall temperature on high-temperature convection heating surface of utility boiler based on the thermal deviation and compile an on-line monitoring system.For the overheat and tube explosion on supetheater and reheater,this dissertation mainly analyzed theoretically the thermal deviation in three aspects that steam, gas and the heat deviation on the same panel tubes and made a series of improvements on the present computing model of tube wall temperature based on the previous research results. The verifiable subsection-calculating model which takes total heat-absorption in whole pipe loop as thermal restrictive condition was put forward. It also deduced and amended Angle Factor and Radiation Factor which will be used in the temperature calculation. Furthermore, the reasons of tube rupture were also discussed, and the long-term high temperature creep of tube metal was regarded as the primary cause of the heating surface failure. The paper analyzed and selected the high temperature creep remaining life calculation method which will be practicable under the on-line monitoring condition.In order to test the proposed theory and computing method, the applied calculation including tube wall temperature and creep remaining life were conducted on the hider-screen superheater and the high-temperature reheater of a 600MW subcritical boiler. Due to the above work,the on-line system applied in aforesaid boiler to monitor tube wall temperature on high-temperature convection heat transfer surface was exploited.