Process modelling, simulation and optimisation of natural gas combined cycle power plant integrated with carbon capture, compression and transport

Luo, Xiaobo

Abstract

Reducing CO₂ emissions from fossil fuel-fired power plants is a significant challenge, technically and economically. Post-combustion carbon capture (PCC) using amine solvents is widely regarded as the most promising technology that can be commercially deployed for carbon capture from fossil fuel-fired power plants. However, for its application at full commercial scale, the main barrier is high cost increment of the electricity due to high capital costs and significant energy penalty. This thesis presents the studies on optimal design and operation of Monoethanolamine (MEA)-based PCC process and the integrated system with natural gas combined cycle (NGCC) power plant through modelling, simulation and optimisation, with the aim to reduce the cost of PCC commercial deployment for NGCC power plants.

The accuracy of optimisation depends on good predictions of both process model and economic model. For the process modelling, the philosophy with its framework was analysed for this reactive absorption (RA) process. Then the model was developed and validated at three stages. In the first stage, the predictions of thermodynamic modelling were compared with experimental data of CO₂ solubility in aqueous MEA solutions. The results show the combination of correlations used in this study has higher accuracy than other three key published contributions. Then key physical properties of MEA-H₂O-CO₂ system were also validated with experimental data from different publications. Lastly, a steady state process model was developed in Aspen Plus® with rate-based mass transfer and kinetic-controlled reactions. The process model was validated against comprehensive pilot plant experiment data, in terms of absorption efficiency and thermal performance of the integrated system.

The cost model was developed based on the major equipment costs provided by vendors after detailed engineering design in a benchmark report. The uncertainty of this method could be in the range of from −15% to 20%, instead of other empirical methods with uncertainty of from −30% to 50%. The cost model was integrated into the process model by coding Fortran subroutine in Aspen Plus®. Using this integrated model, the optimisation studies were carried out for the PCC process only. The impact of key variables variation was also analysed.

Subsequently, the scope of this study was extended to cover different sections of the integrated system including a 453MWe NGCC power plant, PCC process, CO₂ compression trains and CO₂ transport pipeline network. For the integration of NGCC power plant with PCC process and CO₂ compression, exhaust gas recirculation (EGR) technology was investigated and showed significant economic benefit. A specific supersonic shock wave compressor was adopted for the CO₂ compression and its heat integration options with power plant and PCC process were studied.

For the study on the CO₂ transport pipeline network planned in the Humber region of the UK, a steady state process model was developed using Aspen HYSYS®. The process model was integrated with Aspen Process Economic Analyzer® (APEA), to carry out techno-economic evaluations for different options of the CO₂ compression trains and the trunk onshore/offshore pipelines respectively. The results show the optimal case has an annual saving of 22.7 M€ compared with the base case.

In the end, optimal operations of NGCC power plant integrated with whole carbon capture and storage (CCS) chain under different market conditions were studied. Levelised cost of electricity (LCOE) is formulated as the objective function. The optimal operations were investigated for different carbon capture level under different carbon price, fuel price and CO₂ transport and storage (T&S) price. The results show that carbon price needs to be over €100/ton CO₂ to justify the total cost of carbon capture from the NGCC power plant and needs to be €120/ton CO₂ to drive carbon capture level at 90%. The results outline the economic profile of operating an NGCC power plant integrated with CCS chain. It could help power plants operators and relevant government organizations for decision makings on the commercial deployment of solvent-based PCC process for power plans.

Citation

Luo, X. (2016). Process modelling, simulation and optimisation of natural gas combined cycle power plant integrated with carbon capture, compression and transport. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4218648

• Thesis Type: Thesis
• Deposit Date: Nov 4, 2016
• Publicly Available Date: Feb 23, 2023
• Keywords: Engineering
• Public URL: https://hull-repository.worktribe.com/output/4218648
• Additional Information: School of Engineering, The University of Hull
• Award Date: May 1, 2016