Volume 57

Research on phase behavior, flow assurance, and energy efficiency optimization in the reinjection transport process of impurity-containing CO₂ Jiao Zhou, Xuewen Cao, Xingwang Zhang

Abstract

The reinjection technology of impurity-containing CO₂ represents a critical challenge to the safety and economic viability of carbon capture and storage (CCS) systems. This study systematically analyzes the influence patterns of impurities on CO₂ phase behavior, flow characteristics, and reinjection energy consumption through the establishment of thermodynamic phase equilibrium models, flow assurance models, and energy consumption optimization models. By utilizing the Peng-Robinson (PR) equation of state and Aspen HYSYS software, the differential regulatory mechanisms of various impurities (e.g., N₂, H₂) on CO₂ critical point shifts, phase envelope expansion, and property parameters (density, viscosity, thermal conductivity) was revealed. Through OLGA multiphase flow simulations, we quantified the low-temperature risks induced by the Joule-Thomson effect and hydrate formation potential, demonstrating that impurity-containing CO₂ exhibits 2.66 °C less throttling temperature drop compared to pure CO₂, with the critical hydrate formation temperature decreasing from 10 °C to 8 °C. For the Snohvit field case in Norway, a reinjection scheme integrating four-stage compression with interstage air cooling optimization was proposed. This high-temperature reinjection strategy (50 °C) achieved 24.8% lower total energy consumption than conventional low-temperature injection (20 °C), while recommending further efficiency improvements through waste heat recovery and intelligent control. The findings provide theoretical foundations and technical pathways for the safe transportation and efficient reinjection of impurity-containing CO₂.

Keywords Impurity-containing CO₂, Phase behavior, Flow assurance, Energy efficiency optimization, Carbon capture and storage (CCS)