The Model And Numerical Simulation Of Heat Transfer In A Rolling-cylinder Type Slag-cooler Of CFB Boiler

CFBC has been applied widely during recent years in the improvement and erection projects of power-plant boilers, because it is adaptable to various fuels, easy to regulate and green to the environment. The high temperature slag of CFB boilers has a great harm to the function of boilers, unless the enormous slag is moved off as soon as possible. Due to these reasons mentioned above, the cooling of high temperature slag is indispensable. Rolling-cylinder type slag-coolers are installed to attain the cooling aim in CFB boilers in many circumstances.In this thesis, the transporting and heat transfer regulations of slag in rolling-cylinder type slag-coolers are revealed, in order to understand the principle of coolers better and to establish the basis of further application.Beginning with the nowadays and future of CFB boilers, the importance and necessity of slag-coolers are analyzed in the thesis. After that, several kinds of slag-coolers are introduced, of which the characteristics are indicated.The research object of this article is a rolling-cylinder type slag-cooler which has radial spiral blades and vertical ribs. The movement rule of slag in rolling-cylinder type slag-coolers is revealed with the meticulous analysis and conclusion. On the basis of above research, a calculation formula which is used to get the transportation quantity in rolling-cylinder type slag-coolers is put forward.There are nine modes in which heat is transferred in the slag-cooler, and the relationship formula for heat transfer coefficient of each mode is given. A one-dimensional-axial heat transfer model is constructed firstly, and a two-dimensional-sectional heat transfer model is also found with introducing a nominal heat conduction coefficient of slag. Simulated calculation is done within the two models which are referred above, and the simulation result is compared with experiment result. The comparison shows that the relationship formulae and heat transfer models which are advanced above are feasible and usable.