Optimization research on the off-design characteristics of partial heating supercritical carbon dioxide power cycle in the landfill gas exhaust heat utilization system

Abstract

• Off-design characteristics of partial heating supercritical CO 2 cycle are studied. • A novel calculation flow chart for the system off-design performance is proposed. • Separation control and inventory control are adopted for the thermal system. • A best control scheme relied on the net power maximization can be determined. Landfill gas waste heat power generation is an effective way to promote the efficiency and economics of power plants. However, the operating performance of the power generation system needs to be improved further. In this paper, a systematic optimization research on the off-design characteristics of the partial heating supercritical carbon dioxide power system for exhaust heat utilization from gas turbine cycle are conducted. Optimal operating conditions in thermodynamics and economics obtained by genetic algorithm are determined as design conditions. Gradient descent method is used to obtain the best operating point under a certain off-design working condition. With the goal of maximizing net power output, separation control and inventory control are applied to the system. The results exhibit that the best thermoeconomic performance can be gained when the pressure ratio is 2.28 with separation ratio of 0.35 at design stage. In the off-design stage, the maximum net power shows an approximately linear growth trend from 1581 kW to 2924 kW with increasing heat source temperature and mass flow rate under the inventory control, while growth rate of net power output gradually decreases under the separation control. Finally, the best control scheme mixed with inventory control and separation control is proposed and determined quantitatively.