Pump Selection in Carbon Sequestration

How to Select the Right Pump for CO₂ Injection in Carbon Sequestration

Introduction

Carbon capture and sequestration (CCS) is a vital technology in the quest to reduce CO₂ emissions. Selecting the right pump for CO₂ injection is crucial to ensure efficiency, reliability, and environmental safety. The key challenges include CO₂ phase transitions, high pressures, and corrosion risks.

Understanding CO₂ Behaviour and Its Impact on Pump Selection

CO₂ Phases and Properties

CO₂ behaves differently in its gaseous, liquid, and supercritical states. Each state presents unique challenges for pump systems. In its gaseous state, CO₂ is highly compressible and has low density. In its liquid state, CO₂ is denser and nearly incompressible but can quickly change to gas if the pressure drops, or the temperature rises, leading to cavitation and other process failures. Supercritical CO₂ behaves like both a gas and a liquid, with high density and low viscosity. Its properties fluctuate rapidly with small changes in temperature and pressure, complicating pump operation. Additionally, supercritical CO₂ acts as a powerful solvent, so pump materials must be resistant to chemical degradation.
Successfully handling CO₂ across these phases requires pumps designed to manage phase changes and density variations. Selecting the right pump – whether for compressible gases, high-pressure liquids, or supercritical fluids – is critical for maintaining system efficiency and preventing equipment failure.

Pressure Requirements

CO₂ injection into deep sequestration reservoirs requires pumps capable of handling high pressures, often exceeding 100 bar, to overcome the pressure in the reservoir and drive the CO₂ underground. These reservoirs are located deep beneath the Earth’s surface, where pressures are significantly higher than at shallower depths. The pumps must generate sufficient pressure to inject CO₂ efficiently and maintain operational integrity under harsh conditions, including high temperatures and variable flow rates. Properly designed pumps ensure the CO₂ remains in a dense phase, minimizing leakage and maximizing storage capacity within the reservoir. Both the typical pressure requirements and the operating conditions for CO₂ subsea sequestration are similar to those for drill cuttings re-injection (CRI). This is an environmentally sound method for disposing of offshore drilling waste and we were instrumental in the development of the early CRI pump units over 25 years ago.

Material Selection for CO₂ Pumps

Corrosion Risks

CO₂ can form corrosive medium, especially when mixed with impurities or formation water, that can attack pump materials. Pumps must be constructed from corrosion-resistant materials to avoid premature failure. At Calder, we emphasize the use of durable and corrosion-resistant materials for CO₂ injection pumps. We focus on using high quality alloys and stainless steel for parts exposed to high pressure CO₂ environments to ensure long-term reliability and durability in challenging conditions.
Advanced corrosion modelling is essential to predict material degradation in CO₂ injection environments, helping to select the most suitable materials and design strategies to prolong pump life and ensure safe CO₂ injection.

Operational Challenges in CO₂ Injection for Carbon Sequestration

Handling High Pressure Conditions

CO₂ injection presents several operational challenges, particularly due to the high pressures and possible phase transitions involved. Managing pressure requirements – CO₂ needs to be pressurized to levels often exceeding 100 bar for deep sequestration – requires pumps capable of handling high pressures while maintaining system integrity. Liquid CO₂ has a far higher compressibility than water, and this needs to be considered during pump and equipment specification.

Energy Efficiency Considerations

The energy demand of operating pumps for long durations can be significant. Selecting energy-efficient pumps and implementing strategies to reduce operational costs are crucial. We design pumps that minimize energy consumption while maximizing flow rates and performance, leading to substantial operational cost savings.

Carbon Sequestration Case Studies and Real-World Examples

Offshore and Subsea CCS Projects

Offshore and subsea CCS projects face harsh environmental conditions, making pump reliability and material choice critical. We have extensive experience in designing and manufacturing pumps for such challenging environments, ensuring robust performance and durability.

Lessons from Material and Corrosion Control Studies

Real-world applications of material selection and corrosion management strategies highlight the importance of choosing the right materials and sealing systems to prolong pump life and ensure safe CO₂ injection. We leverage advanced materials and corrosion control techniques to enhance pump performance and reliability.

Conclusion

Selecting the right pump for CO₂ injection in sequestration applications involves understanding CO₂ properties, choosing the right materials, ensuring energy efficiency, and maintaining safety standards. As technology progresses, advanced pump design and materials will play a pivotal role in advancing carbon capture and storage efforts, ultimately contributing to global climate goals. We are committed to innovation and performance enhancement, overcoming the challenges associated with CO₂ injection, and ensuring the long-term success of CCS initiatives.

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