Nonlinear Dynamic Model of a Fluidized-Bed Steam Generation System

Abstract

A dynamic model of an atmospheric pressure fluidized-bed steam generation system is presented which allows digital simulation and analytical controller design. The nonlinear, time-invariant, deterministic, continuous-time model is derived in state-space form from conservation relations, empirical correlations and system design data. The model has been verified for steady-state and transient performance with measured data from experimental test runs. Transient responses of several process variables, following independent step disturbances in coal feed rate and air flow, are illustrated.

Transient modelling of operational upsets in a special-purpose boiler

“…The primary equations in the model are those that govern mass-and energy-conservation in each of the control volumes. The particular forms of these equations, which depend on the type of control volume in question, are the same as in the earlier-reported work (Robinson, 1982). In Model TBMSOO, this set of equations consists of 43 first-order ordinary differential equations and 69 algebraic equations.…”

“…The study described in this paper concerned the further development and use of a previously-described model of boiler operation (Robinson, 1982). In the earlier work, and in the present study, attention was focused on the development of models that predict a relatively high level of detail within a boiler.…”

“…Of the latter control volumes, 11 contain either liquid or a liquid-vapour mixture that is predominantly liquid, and the other 12 contain either vapour or a liquid-vapour mixture that is predominantly vapour. The methodology used to identify the control volumes is the same as in the earlier-reported work (Robinson, 1982). Figure 2 is a schematic diagram of the thermodynamic control volumes, each represented by a circle or rectangle, together with the mass flows and heat flows that cross the control-volume boundaries.…”

“…The other is a similar mode for shut-down operation which is designed to gradually lower the pressure. The former of these was described briefly in the earlier report (Robinson, 1982). Excess air is also treated in a special way.…”

“…Models focusing exclusively on a boiler, and which therefore are especially germane to the work reported here, have also been described. A few examples are a detailed model of a once-through boiler (Doverman et al, 1981), a similar model of a drum-type boiler (Robinson, 1982), and a model of a drum-type steam generator used in connection with a gas-cooled nuclear reactor (Longworth et al, 1982). Transient modelling of less-conventional power plant equipment has also been reported, with some recent examples being work on fluidized-bed boilers (Ray et al, 1980), solar energy steam generators (Bau and Torrance, 1981;Ray, 1981), and closed-cycle gas turbine power plants (Bammert and Poesentrup, 1980).…”