Regulatory Control of Amine Scrubbing for CO2 Capture from Power Plants

Tight integration between the amine scrubbing plant, coal-fired power plant, and enhanced oil recovery (EOR) facility creates process design and control challenges for post-combustion CO2 capture. A dynamic model of an advanced amine scrubbing process and a steady state model of a 550 MWe power plant were used to examine four bounding cases that represent different system components dominating the regulatory process control strategy. Satisfying the operational and economic objectives of one system component resulted in unfavorable dynamic performance for the remainder of the system. When a step change decrease occurred in either the CO2 delivery rate from the capture plant to the EOR facility or the steam extraction rate from the power plant to the capture plant, more than 3 h was required for the amine plant to reach a new steady state. Attempting to control the CO2 removal rate from the flue gas can not be satisfactorily achieved through regulatory control alone. Controlling stripper temperature and pressure brought all manipulated variables to within 5% of their final steady state value in less than 2 h in response to a decrease in power plant load. The design of process equipment, specifically the CO2 stripper and steam extraction valve, depends heavily on the desired process control strategy. The solvent surge tank should be placed in the flow of the rich solvent to allow for tighter control of absorber removal, although the difference in system performance between rich and lean surge tanks was found to be negligible when the surge tank inventory was small.