Validation of a Dynamic Model of the Brindisi Pilot Plant

Abstract In this work, a dynamic model of the Brindisi CO2 capture pilot plant is implemented in K-spice general simulation tool. The model is used to simulate relevant step changes performed during a pilot plant campaign conducted in the EU project Octavius in May and June 2013. Model results are compared to dynamic pilot plant data and it shows good transient agreement to the experimental results. The model is therefore able to capture the main process dynamics. An offset is, however, observed in some cases, especially during the initial simulation time. This is most likely caused by the fact that the model was given a steady state starting point, while the pilot plant was not necessarily completely at steady state when the step change was introduced. It is challenging to ensure steady state conditions prior to dynamic tests in a pilot plant, especially for one that is connected to a real power production unit as this one. Power production variations will act as disturbances to the capture unit, and due to slow transients in the solvent inventory of the capture unit, it will take several hours to ensure steady state conditions with stable inlet flue gas conditions

A numerical solution strategy for dynamic simulation of post-combustion CO2 capture

This paper describes in detail the numerical solution of a dynamic process developed for post-combustion absorption based CO2 capture. The method used in this work is sequential modular integration. This means that each process unit is modeled and integrated individually while co-ordination algorithms are developed to synchronize process units in time and provide input between connecting units. A pressure-flow interaction algorithm (p-f network solver) is also developed to provide estimates of downstream pressures for each unit. This is required in order to calculate the outlet flow from the units. The complete process plant model is developed to enable simulation of the post-combustion CO2 capture process at power plant load variations. Two examples of load variations are presented in this paper.publishedVersio

Experimental results of transient testing at the amine plant at Technology Centre Mongstad: Open-loop responses and performance of decentralized control structures for load changes

Flexible operation of combined cycle thermal power plants with chemical absorption post combustion CO2 capture is a key aspect for the development of the technology. Several studies have assessed the performance of decentralized control structures applied to the post combustion CO2 capture process via dynamic process simulation, however there is a lack of published data from demonstration or pilot plants. In this work, experiments on transient testing were conducted at the amine plant at Technology Centre Mongstad, for flue gas from a combined cycle combined heat and power plant (3.7–4.1 CO2 vol%). The experiments include six tests on open-loop responses and eight tests on transient performance of decentralized control structures for fast power plant load change scenarios. The transient response of key process variables to changes in flue gas volumetric flow rate, solvent flow rate and reboiler duty were analyzed. In general the process stabilizes within 1 h for 20% step changes in process inputs, being the absorber column absorption rates the slowest process variable to stabilize to changes in reboiler duty and solvent flow rate. Tests on fast load changes (10%/min) in flue gas flow rate representing realistic load changes in an upstream power plant showed that decentralized control structures could be employed in order to bring the process to desired off-design steady-state operating conditions within (<60 min). However, oscillations and instabilities in absorption and desorption rates driven by interactions of the capture rate and stripper temperature feedback control loops can occur when the rich solvent flow rate is changed significantly and fast as a control action to reject the flue gas volumetric flow rate disturbance and keeping liquid to gas ratio or capture rate constant

Dynamic Process Model Validation and Control of the Amine Plant at CO2 Technology Centre Mongstad

This paper presents a set of steady-state and transient data for dynamic process model validation of the chemical absorption process with monoethanolamine (MEA) for post-combustion CO2 capture of exhaust gas from a natural gas-fired power plant. The data selection includes a wide range of steady-state operating conditions and transient tests. A dynamic process model developed in the open physical modeling language Modelica is validated. The model is utilized to evaluate the open-loop transient performance at different loads of the plant, showing that pilot plant main process variables respond more slowly at lower operating loads of the plant, to step changes in main process inputs and disturbances. The performance of four decentralized control structures is evaluated, for fast load change transient events. Manipulation of reboiler duty to control CO2 capture ratio at the absorber’s inlet and rich solvent flow rate to control the stripper bottom solvent temperature showed the best performance

Dynamic modeling of the solvent regeneration part of a CO2 capture plant

In this work, a system of unit operations is modeled and implemented in MATLAB for dynamic simulation of the regeneration part of the CO2 capture process. The system consists of a stripper, a reboiler and a condenser, and it is solved by a simultaneous equation based method. The method proves to be suitable for solving the regeneration part of the CO2 capture process and it shows numerically stable behavior in general. Further, two dynamic simulation cases are carried out and compared to steady state simulation results from CO2SIM. The dynamic simulation results show reasonably good agreement with steady state simulations, even though a very simplified flash tank model is used for simulation of reboiler and condenser and a simplified thermodynamic model is applied compared to the more robust CO2SIM model. Due to lack of dynamic pilot data, validation of the dynamic regeneration model has been difficult at this point. However, this is necessary for a thorough validation of the model for transient conditions

A numerical solution strategy for dynamic simulation of post-combustion CO2 capture

This paper describes in detail the numerical solution of a dynamic process developed for post-combustion absorption based CO2 capture. The method used in this work is sequential modular integration. This means that each process unit is modeled and integrated individually while co-ordination algorithms are developed to synchronize process units in time and provide input between connecting units. A pressure-flow interaction algorithm (p-f network solver) is also developed to provide estimates of downstream pressures for each unit. This is required in order to calculate the outlet flow from the units. The complete process plant model is developed to enable simulation of the post-combustion CO2 capture process at power plant load variations. Two examples of load variations are presented in this paper

A numerical solution strategy for dynamic simulation of post-combustion CO2 capture

This paper describes in detail the numerical solution of a dynamic process developed for post-combustion absorption based CO2 capture. The method used in this work is sequential modular integration. This means that each process unit is modeled and integrated individually while co-ordination algorithms are developed to synchronize process units in time and provide input between connecting units. A pressure-flow interaction algorithm (p-f network solver) is also developed to provide estimates of downstream pressures for each unit. This is required in order to calculate the outlet flow from the units. The complete process plant model is developed to enable simulation of the post-combustion CO2 capture process at power plant load variations. Two examples of load variations are presented in this paper

Dynamic modeling of the solvent regeneration part of a CO2 capture plant

In this work, a system of unit operations is modeled and implemented in MATLAB for dynamic simulation of the regeneration part of the CO2 capture process. The system consists of a stripper, a reboiler and a condenser, and it is solved by a simultaneous equation based method. The method proves to be suitable for solving the regeneration part of the CO2 capture process and it shows numerically stable behavior in general. Further, two dynamic simulation cases are carried out and compared to steady state simulation results from CO2SIM. The dynamic simulation results show reasonably good agreement with steady state simulations, even though a very simplified flash tank model is used for simulation of reboiler and condenser and a simplified thermodynamic model is applied compared to the more robust CO2SIM model. Due to lack of dynamic pilot data, validation of the dynamic regeneration model has been difficult at this point. However, this is necessary for a thorough validation of the model for transient conditions