This study aims to investigate the applicable conditions and key operational parameters for an integrated compression, purification, decarbonization, and denitrification process applied to natural gas oxy-fuel combustion flue gas. The research seeks to clarify the technical feasibility and performance boundaries of this process for achieving efficient carbon dioxide (CO₂) capture coupled with deep removal of nitrogen oxides (NO_x), providing a practical solution for integrated carbon capture and pollutant control in natural gas oxy-fuel combustion systems.

A steady-state process model for the compression and purification of oxy-fuel combustion flue gas was developed using Aspen Plus, which accurately describes the thermodynamic behavior of the high-pressure, multi-component gas mixture. Through systematic simulation and parametric sensitivity analysis, the study focused on the combined effects of the initial CO₂ volume fraction in the flue gas and the system operating pressure on process performance. Key performance indicators evaluated include the CO₂ recovery rate, liquid CO₂ product purity, NO_x removal efficiency, and specific comprehensive power consumption.

The simulation results establish a definitive and strong correlation between the CO₂ recovery efficiency and the initial concentration of CO₂ in the flue gas. A clear technical threshold is identified: to attain a CO₂ recovery rate of 80% or higher, the initial CO₂ volume fraction must exceed 60%. This finding defines a primary applicability criterion for the compression-purification approach. Subsequent analysis concentrated on flue gas compositions meeting this high-concentration criterion (>60% CO₂). Within this domain, the system operating pressure emerges as the most influential parameter governing the synergistic relationship between NO_x abatement and CO₂ purification efficiency. Detailed parametric optimization reveals a distinct optimal operating pressure of 2.8 MPa. Operating at this pressure enables the process to achieve superior performance across all key metrics: the NO_x removal efficiency surpasses 94%, the purified liquid CO₂ product attains a purity of 95% or higher, and the target CO₂ recovery rate of ≥80% is reliably maintained. Crucially, this operating point corresponds precisely to the minimum in specific power consumption, which is quantified at 120.1 kW·h per ton of CO₂ captured. This represents an optimal trade-off, balancing high environmental performance with minimized energy penalty, a critical factor for economic feasibility.

The compression and purification technology is suitable for treating oxy-fuel combustion flue gas with a high initial CO₂ volume fraction (>60%). By optimizing the system pressure to 2.8 MPa, efficient CO₂ capture and deep NO_x removal can be achieved simultaneously with low energy consumption. This study clarifies the key performance thresholds and optimal operating parameters for this integrated process, providing a concrete and feasible technical solution for achieving pollution reduction, carbon mitigation, and resource utilization in natural gas oxy-fuel combustion systems.