At present

there are lacks of rapid adjustment performance and deep adjustment performance in flue gas desulfurization systems

so that flexibility transformation should be carried out for the slurry circulating system. In this study

the calculation model of slurry circulating pipeline was established

and the flexibility adjustment range for slurry circulating system was calculated according to the equipment situation of a 330 MW coal-fired power unit. Meanwhile

adjustment performance test after the transformation was carried out. The results show that

the adjustment performance and energy saving effect of the slurry circulating system depend on its flexibility adjustment range

which should be calculated before the transformation. The flexibility transformation improves the safety and stability of the desulfurization system

which has certain linear and rapid adjustment performance by following the fluctuation of SO_2 mass concentration in raw flue gas and unit load

as well as certain deep adjustment performance. The slurry circulating system with the mode of one inverter for two motors can make the flexibility adjustment in a better state. There is obvious energy saving effect after the transformation in this unit

of which the cost can be recovered in 1.1 years

but the cost recovery cycle for different units will be different. The conclusion of this study can provide a guidance for flexibility transformation of slurry circulating systems and operation optimization of desulfurization systems.