Development and technical progress in large-scale circulating fluidized bed boiler in China
FRONTIERS IN ENERGY
Authors: Huang, Zhong; Deng, Lei; Che, Defu
Abstract
Circulating fluidized bed (CFB) boilers has realized the clean and efficient utilization of inferior coal like gangue and coal slime, high sulfur coal, anthracite, petroleum coke, oil shale and other resources. As a country with the largest amount of CFB boilers and the largest installed capacity in the world, China has 440 100-600 MWe CFB boilers with a total capacity of 82.29 GW(e), including 227 units of 135 MWe, 95 units of 300 MWe, and 24 supercritical units. The statistics of typical 100-300 MWe CFB boilers showed that the average number of unplanned shut-down was only 0.37 times per year, among which the 135 MWe was 0.26 times per year and 300 MWe was 0.46 times per year. The auxiliary power ratio of some 300 MWe CFB boilers based on flow-pattern reconstruction can be reduced to about 4%, which is closed to the same level of pulverized coal (PC) boilers. This paper summarizes the development process and application status of China's large-scale CFB boilers, analyzes the characteristics and technical performance of the iconic units, and introduces solutions to the problems such as water wall wear and bottom ash cooling.
Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed
PROCESSES
Authors: Wang, Min; Wu, Yingya; Shi, Xiaogang; Lan, Xingying; Wang, Chengxiu; Gao, Jinsen
Abstract
With the development of computing power, the simulation of circulating fluidized bed (CFB) has developed from riser-simplified simulation to riser-only simulation, then to full-loop simulation. This paper compared these three methods based on pilot-scale CFB experiment data to find the scope of application of each method. All these simulations, using the Eulerian-Eulerian two-fluid model with the kinetic theory of granular theory, were conducted to simulate a pilot-scale CFB. The hydrodynamics, such as pressure balance, solids holdup distribution, solids velocity distribution, and instantaneous mass flow rates in the riser or CFB system, were investigated in different simulations. By comparing the results from different methods, it was found that riser-simplified simulation is not sufficient to obtain accurate hydrodynamics, especially in higher solids circulating rates. The riser-only simulation is able to make a reasonable prediction of time-averaged behaviors of gas-solids in most parts of riser but the entrance region. Further, the full-loop simulation can not only predict precise results, but also obtain comprehensive details and instantaneous information in the CFB system.