Flow characteristics and flow rate prediction of pulverized coal through a regulation valve

Abstract

• The optimum valve sweeping gas fraction was determined. • Control characteristics of the regulation valve were studied. • Limit operating conditions of the regulation valve were defined. • A semi-empirical model was established for pulverized coal flow rate prediction. In this paper, experiments of dense-phase pneumatic conveying of pulverized coal were carried out in an industrial-scale system to study the control characteristics of the regulation valve and to predict the solid mass flow rate. Firstly, effects of valve sweeping gas on conveying stability and solid mass flow rate were investigated and the optimum valve sweeping gas was determined. Second, effects of valve opening on pressure distribution and solid mass flow rate were investigated by conducting experiments at different conveying pressure drops and different valve openings. A good linear relationship between the valve pressure drop ratio and the valve opening was found, and as the valve opening increased from 13 % to 70 % the solid mass flow rate increased gradually. Limit operating conditions of the regulation valve including flow blockage and control failure were consequently determined and analyzed. Finally, a robust model was established to predict the solid mass flow rate by introducing the valve sensitivity coefficient into the traditional pressure drop ratio model. The model can predict the solid mass flow rate well by providing errors mostly within ± 10 %. This study will provide certain reference for solid mass flow rate regulation in the dry coal gasification process.