Modelling of a batch-fired straw boiler for control of the combustion chamber temperature

The paper proposes a batch-fired straw boiler model, which is used to control the temperature of the combustion chamber. This model describes a boiler which consists of a combustion chamber and a water jacket. The combustion chamber is blown by the adjustable air mass flow, which is used for straw combustion in the combustion chamber. The combustion chamber heats a water jacket, which in turn transfers heat to the external circulation. The model is nonlinear because of the straw combustion process. Apart from this process, the other components of the model are linear and describe mass and heat transfer. The boiler model has single input and single output (SISO). The input of the model is the air mass flow and the output is the temperature of the combustion chamber. Based on the presented model, one proposed a closed-loop system to control the temperature of the combustion chamber. The closed-loop system consists of the classical PID controller, model of the whole plant and some inverse transfer function of the nonlinear part of the whole model. In this way, there is calculated a time response of the air mass flow, which results a reference value of the temperature of the combustion chamber. The paper presents results of simulation of this closed-loop system in MATLAB/Simulink.