Background: The research works on circulating fluidized bed are mostly devoted
to investigation of the process in separate parts of a circulating fluidized bed reactor, and
practically never to investigation of the entire circulating loop. The interference between the
processes in the riser, separator and downer remains practically unexamined.
Objective: The objective of the study is to develop a simple yet informative model to investigate
the features of a particulate flows forming in a circulating gas-solid fluidized bed reactor.
Method: The method of mathematical modeling is used. The proposed model is based on the
theory of Markov chains. The transformation of a raw particulate material into an end product
in the riser is taken into account. The return flow in a downer is described with a time delay
between the inflow and outflow from it.
Results: The proposed model allowed performing numerical experiments on the influence of
the process parameters on its main technological characteristics both for the transient and
Conclusion: It is found that the batch circulating fluidization has advantages in comparison to
the dense bed only at a small time delay in the downer and a relatively high gas flow velocity
in the riser. It is also found that the maximum feed flow rate exists in a continuous circulating
fluidization that ensures the stable operation of the circuit. This threshold crossing leads to
the overfilling of the riser and its blockage. Optimal positioning of the return flow input allows
increasing this maximum feed flow rate.