Distributed Dynamic Model And Metal Temperature Calculation Of Rear Platen Superheater

Superheater is a component of boiler thermal system while rear superheater is one of the main parts of superheater, which is generally arranged in the top of furnace chamber and suffered with scouring and radiating of high temperature flue gas secular. Therefore, the heat exchange situation of rear superheater is much badly and temperature exceeding and pipe explosion frequently occur. In order to avoid the occurrence of these phenomenons, two-dimension distribution of pipe screen metal wall temperature and inner pipe working media status parameters of rear superheater should be known, which requires us to establish detailed distributed dynamic mathematic model of boiler rear superheater.In this essay, the study actuality and development of modeling and simulation of boiler thermodynamic system is reviewed at first. Some basic knowledge of modeling and simulation of thermodynamic system is introduced too, such as theoretic base of modeling and simulation, basic methods of modeling, distributed parameter model and lumped parameter model, basic procedure of modeling and simulation, and so on.In order to understand the operation safety and pipe service life span of rear superhearter, the essay established dynamic mathematic model of single piece of screen of rear superhearter, including the following sub-models: flue gas side model, steam side and metal pipe wall mathematic model, flow calculation model and wall temperature calculation model.Through established dynamic mathematic model, calculation program is worked out to apply for simulation calculation. Setting the real supoerheater of a 300MW controlled circulation boiler as the simulation objection, steam flow distribution of each pipe under steady state are given as well as inner pipe steam state parameters, inside and outside pipe wall temperature and two-dimensional temperature distribution of pipe dirt fouling layer. According to the compare of some calculated values of key parameters with designed values, it is proved that the model has good precision and based on which, change process of steam flow, pipe inlet steam temperature and inner pipe steam temperature when pipe outside flue gas side heat exchange quantity changes are simulated. Simulation results are analyzed which basically correctly reflect dynamic characteristic of rear superheater, and then through calculation of pipe metal outside temperature, specified places of inner screen metal pipe wall with largest probability of occurring temperature exceeding and pipe exploring are pointed out and some solutions are given.Finally, the essay gives the summary of overall work, at the same time the farther work and advice were provided.