In order to analyze the economy of gas-supercritical carbon dioxide(S-CO_2) combined cycle system

based on the cascade cycle

this article designs 12 schemes with different cooler stages

different numbers of flue gas-S-CO_2 heat exchangers and different numbers of shunt pipes

and optimizes the parameters of each scheme using the genetic algorithm. Finally

it screens out the best scheme with the optimum economic performance. The results show that

the cycle efficiency of the system increases with the cooler stages

the number of flue gas-S-CO_2 heat exchangers and the number of shunt pipes. From the perspective of the degree of improvement of the cycle efficiency

the order of the measures is: increasing the number of the flue gas-S-CO_2 heat exchanger increasing the number of the shunt pipeline increasing the cooler stages. Moreover

with the increase of the cooler stages

the flue gas-S-CO_2 heat exchangers' number and the shunt pipelines' number

the degree of increase in cycle efficiency decreases. Among the designed 12 schemes

scheme 5 has the highest total economic benefit(0.52 billion yuan for 20 years' operation)

namely the two-stage cascade cycle equipped with a two-stage cooler.