Novel coordinated control method with coal-quality correction of circulating field bed boiler
To improve the load-following capability and the coal-quality applicability of a circulating field bed boiler (CFBB), a new coordinated control method with coal-quality correction is proposed in this paper. This method takes the primary air as another new control variable into the coordinated control of CFBB, which can take advantage of the unburned carbon in bed to improve its load-following capability. Simultaneously, a multivariable predictive controller based on augmented state space model is designed to deal with the CFBB's characteristics such as time-delay and strong coupling. Finally, an improved strategy to correct coal-quality online based on the disturbance observer is provided. Compared with the conventional control scheme, the simulation results for a 330MW CFBB shows that the method proposed in this paper can significantly improve the load-following capability and the coal-quality applicability.
A Steam-Temperature Adaptive Series-Step Control System for Circulating Fluidized Bed Boilers of Giant Domestic Manufacture
Due to the high order, the lag and the varying parameter characteristics of the steam temperature for circulating fluidized bed boilers (CFBB) and the full-coefficients adaptive control theory, a steam temperature adaptive series-step control system is put forward. The control system effectively eliminates the harmful effects caused by the controlled object's the high order and the lag and the varying parameter characteristics. The system is simple and practical, and has an engineering value. The system is applied to a worksite and good control result is obtained. Figs 5, table 2 and refs 2.
Techno-economic analysis of solar thermal power plants using liquid sodium as heat transfer fluid
Abstract Solar thermal power plants with central receiver and thermal storage are expected to be one key technology in future electricity generation, because they are renewable and due to the thermal storage independent of the current solar radiation. State-of-the-art solar power plants often use molten nitrate salts as heat transfer fluid. The use of liquid sodium instead leads to lower electricity generation costs. Sodium has a high thermal conductivity and thus large heat transfer rates are possible. Hence, a smaller absorber surface is sufficient for the same thermal power. As a result, the sodium receiver achieves a higher efficiency at lower investment cost. Additionally, the aiming strategy, which reduces the peak heat flux on molten salt receivers isn’t necessary for sodium. Even at high heat flux densities, the absorber tubes will be cooled sufficiently due to the high heat transfer coefficients. Therefore, the sodium receiver in this analysis is designed for one single aim point, resulting in a heat flux density of q mean = 1.06 MW / m 2 and q peak = 2.99 MW / m 2 . The state-of-the-art system with molten salt considers q mean = 0.51 MW / m 2 and q peak = 1.0 MW / m 2 . The presented techno-economic analysis of two sodium based concepts compared to a reference system with molten salt results in up to 16% lower electricity generation costs.