Plantwide Control of CO₂ Capture by Absorption and Stripping Using Monoethanolamine Solution

Abstract

In this work, plantwide control of an absorption/stripping CO 2 capture process using monoethanol-amine was investigated using dynamic simulation. In this system, CO 2 removal ratio is influenced by operating variables such as lean solvent rate and lean solvent loading, which is in-turn determined by reboiler duty in the stripper. Moreover, we found that the long-term stability of the system cannot be achieved unless the water balance is properly maintained. Hence the following control structure was proposed. In this scheme, the CO 2 removal target is guaranteed using the lean solvent feed rate to the top of the absorber column. The overall water inventory was maintained by controlling the liquid level in the reboiler of the stripping column using makeup water. In order to operate the process with an appropriate lean solvent loading, the temperature at the bottom of stripper is controlled by the reboiler duty. This control structure was tested by disturbances involving inlet flue gas flow, CO 2 concentrations, and H 2 O concentrations as well as changes in removal targets. Dynamic simulations showed that the system can achieve removal targets and stabilize quickly while keeping optimum lean loading constant. To ensure minimum energy consumption, optimizing control can be carried out by adjusting the set point of the reboiler temperature.

Dynamic simulation of MEA absorption process for CO2 capture from power plants

“…Also, the reboiler heat duty has also been proposed by previous control studies to control the reboiler temperature, e.g., Lawal et al (2010) and Lin et al (2011). The other input variable that can be considered as manipulated variable is the valve stem position that regulates the amount of lean liquid solvent flow rate that enters at the top absorber column.…”

“…Accordingly, the lean solvent flow rate directly affects the CO 2 absorbed in this process can be potentially used to control the percentage of CO 2 absorbed. The previous control studies of the MEA absorption process published in the literature also manipulate the lean solvent flow rate to control the percentage of CO 2 absorbed in the absorber column (Lawal et al, 2010;Lin et al, 2011).…”

Process control strategies for flexible operation of post-combustion CO 2 capture plants

“…Tables 2 and 3 present the electricity generated in the coal and gas power plants respectively with and without capture and compression. [35]. In this study we follow this 270 principle, and consider two alternative strategies for controlling the CO 2 capture rate.…”

“…The dynamic modelling and controllability analysis of the integrated power and capture plant is therefore highly important in this context. Most studies in the literature consider individually the capture plant, or even discrete parts of the capture plant such as the absorber and stripper for control, while in this study the integrated coal 35 and gas power plants with post-combustion are considered [6], [7], [8], [9], [10], [11].…”

Dynamic modelling and control of a pilot plant for post-combustion CO2 capture

“…Ziaii et al (2011) developed a rate-based model of the capture process using Aspen Custom Modeler and used it to maximize the power plant profit at different prices of electricity and CO 2 . Lin et al (2011) studied the dynamics of the absorption-regeneration loop in Aspen Plus Dynamics and stated that the control of the process water balance was essential for system long-term stability. Panahi and Skogestad (2011) developed a Unisim model to identify the best control variables for achieving optimal CO 2 removal.…”