Simulation Model for the Model-Based Control of a Biofuel Dryer at an Industrial Combined Heat and Power Plant

Abstract

The primary aim of this article is to present a simulation model for a bark dryer integrated into a combined heat and power plant. The same model can be used for the model-based control of the dryer. The secondary aim is to evaluate how useful the control is from an economic point of view. Results show that the final fuel moisture content can be stabilised by controlling the drying temperature(s). On the other hand, the deviation in final bark moisture decreases even when the dryer has no control at all. Net incomes resulting from drying increase in most cases compared to dryers without control. The need for control cannot be justified on economic grounds.

Keywords:

• Bark drying
• Fixed bed dryer
• Integrated pulp and paper mill

Notes

Design values similar in all cases: Initial bark moisture content 1.53 kg/kg_dm, bed thickness 200 mm, air velocity per free sectional are 0.65 m/s, outdoor temperature 5°C, humidity 0.004 kg/kg_da, effectiveness for secondary heat exchanger 0.89, effectiveness for back-pressure steam exchanger 0.73, effectiveness for extraction steam exchanger 0.67.