Dynamic analysis of the boiler drum of a coal-fired thermal power plant

Abstract

The subcritical coal-fired boilers of thermal power plants consist of a combustion chamber, economizer unit, drum unit (drum, riser, and downcomer), superheater unit (primary superheater, secondary superheater, and final superheater), and reheater unit. The input and output of these units are highly interactive in nature. The efficiency of the subcritical plants is only around 33%. The efficiency needs to be increased to produce more power for the increasing demand, which can be achieved only by implementing supercritical technology or ultra-supercritical technology. However, the conversion of existing subcritical power plants to supercritical power plants is impossible due to the installation cost. So in order to increase the overall efficiency of the existing subcritical power plants, boilers of such units must be examined in order to find safer operational practices. This paper highlights the mathematical modeling of the economizer unit and drum unit of boiler, which can help in enhancing the performance of the boiler system of the power plant. Mass and energy balances for the integrating boiler units have been formulated using first principle laws. The developed model has then been validated with actual plant data obtained from a 210 MW coal-fired thermal power plant. The performance of the open loop responses of the model are analyzed and are included in the results and discussion of the paper. The model provides support for level, pressure, and temperature measurements and predictions. The effect of changes in the parameters of the boiler are studied and discussed in detail.

Dynamic Modeling, Parameter Estimation, and Data Reconciliation of a Supercritical Pulverized Coal-Fired Boiler

“…Within the open literature, subcritical pulverized coal systems have been well-studied using dynamic models, − while transient modeling, simulation, and validation of SCPC power plants are not as prevalent. A few key differences between subcritical and supercritical systems are as follows: SCPC boilers operate under sliding pressure to maximize their efficiency, while subcritical system boilers typically operate under fixed pressure. Due to the sliding-pressure operation of SCPC boilers, they operate under a single phase at full load (i.e., at the highest operating pressure) eventually leading to two-phase operation in different sections of the boiler as the load slides (i.e., under subcritical conditions), while subcritical system boilers operate under constant two-phase conditions.…”

Dynamic modelling and optimal sizing of industrial fire-tube boilers for various demand profiles

“…Hence, in order to accurately simulate the performance of these boilers, their corresponding dynamic behaviour should be simulated. Most of the previous studies on dynamic modelling of boilers have been focused on water-tube units units [2][3][4][5][6][7][8][9][10][11] and very few works have been conducted on fire-tube ones. The studies on water-tube boilers are mainly dedicated to specific aspects of gas/fire side [12] (owing to the importance of heat flux characteristics and temperature distribution [13]) or water/steam sides [9,14,15], along with the control strategy on the water level [16,17].…”

“…Most of the previous studies on dynamic modelling of boilers have been focused on water-tube units units [2][3][4][5][6][7][8][9][10][11] and very few works have been conducted on fire-tube ones. The studies on water-tube boilers are mainly dedicated to specific aspects of gas/fire side [12] (owing to the importance of heat flux characteristics and temperature distribution [13]) or water/steam sides [9,14,15], along with the control strategy on the water level [16,17]. Sørensen et al [18] simulated the dynamic behaviour of the fire-tube boilers employing a modular model consisting of several sub-models, each of which represents a different zone in the boiler.…”