Investigation Of Superheat In High-Temperature Reheater For 300MW Boilers

It is an important technical policy of the electric industrial development of our country to develop the large capacity and high parameter boiler. Because of design and manufacture and all sorts of reasons of management for operation, the operation level of thermal power unit with large capacity in our country is still relatively low, the superheater and reheater of some boilers have been overheated for a long time, which causes the tubes broken. For this reason,some departments such as design and manufacture, operation management and scientific research have already done a large amount of experimental study and improvement research,having made certain effect too, but tubes-broken of the superheater and reheater in large power plants still occurs now and then. The results made of these reasons are the drop of unit's using rate, the rise of cost of electricity-generating and the reduction of operation economy.These factors have seriously influenced the security and economical operation of the unit. This paper firstly summarizes the research background and the general situation of resarch about the overheating problem of boiler's high-temperature surface ,introduces the aspects and research findings in this field such as flux deviation,thermal deviation,flue gas velocity deviation at the exit of furnace and tee bends,et al.Then analyses the reason why high-temperature surfaces are overheated from such aspects as design,manufacture,operation, et al and points out one of the main factors that cause the overheating of reheaters is the flue gas velocity deviation caused by the remaining turning at the exit of furnace. Some experimental researches have been done about overheating problem of the No.1 300MW boiler in zhanjiang power plant.Through the cold and hot experiments,it is pointed out that there exist a high velocity and temperature area at the right lower part.The paper also inspects temperature of the high-temperature reheater's tubes and accounts temperayure's distributing at different measure part of the high-temperature reheater's tubes,analyses the effect of coal , load , temperature of steam at the entrance of reheater,et al, on tubes'temperature. A simulation of the course of combustion is done and we get some results such as the temperature and velocity distribution,the moving track of coal,et al.According to the simulation conclusion,the paper analyses the situation of combustion and at the same time,some factors which will affect the temperature of reheater's tubes are discussed such as the distribution of overfire air,the commission mode of coal grinding machine,the opposing resection angle of upper overfire air,et al.Through the simulation,the paper finds out the main causation that cause the overheat of the high-temperature reheater. Basing on analysis of results from both the experiments and the simulation, the paper puts forward some measure to solve the problems of overheat and flue-gas temperature deviation which will provide some advice for ameliorations in the future.