Nov-2021

Capturing green opportunities

Well-designed post-combustion carbon capture technologies can benefit businesses in the energy sector

Marcel Suhner
Sulzer Chemtech

Article Summary

The capture, sequestration and utilisation of carbon dioxide (CO2) is a key strategy that businesses can adopt to reduce their emissions. By implementing the right technologies, they can meet ambitious climate change mitigation strategies while benefitting from new revenue streams. Sulzer Chemtech offers a cost-effective solution for efficient systems that can maximise the amount of CO2 captured with minimal energy consumption.

Being mostly stationary sources, oil and gas facilities can potentially cut their environmental impact and global warming potential (GWP) by leveraging post-combustion, or post-conversion, carbon capture and storage (CCS) as well as carbon capture, utilisation and storage (CCUS) strategies.

CCS and CCUS solutions remove CO2 from flue gases and store the compound underground or use it in extractive and industrial processes. In CCUS applications, there are multiple opportunities to use the captured CO2, with end uses that vary greatly.¹ For example, the recovered emissions can be used to produce manufactured goods or for enhanced oil recovery (EOR), a method to optimise oil extraction using CO2 to maximise yields in mature wells and store it underground. By utilising or selling the gas for any of these uses, power plants can therefore reduce their environmental footprint while benefitting from additional revenue streams.

How carbon capture works
CCS or CCUS solutions can be added to existing infrastructures, e.g. as part of a retrofit project. Therefore, any processing and manufacturing plant can potentially incorporate these technologies. Moreover, almost all of the CO2 produced on site can be captured using well-designed systems. For instance, Boundary Dam Unit 3 plant in Saskatchewan, Canada, can sequestrate up to 90% of its CO2 emissions.² As a result, highly effective setups can reduce the GWP of power plants by 63-82% per unit of electricity generated, as estimated by lifecycle assessments on CCUS technologies.

The most common process utilised in existing carbon capture systems relies on an amine-based amine scrubbing treatment, whereby CO2 is chemically absorbed onto amine-based solvents. The CO2 rich flue gases enter the bottom of an absorber column, where they make contact with a down-flowing liquid amine-based solvent, such as generic monoethanolamine, methyldiethanolamine or proprietary amine solvents formulation by process licensors. The rich solvent is sent to a stripping column. There, the absorption reaction is reversed (desorption) and the CO2 can be compressed into a supercritical fluid for storage or utilisation, while the lean solvent is recycled to the top of the absorber for reuse.

Maintain peak performance and efficiency
While the process described is established and already utilised in commercial settings, businesses are sometimes reluctant to adopt it because of the capital and operational expenses that may be required. In effect, these systems need to handle particularly challenging separations, as they process high volumes of flue gases that have limited CO2 concentrations. For example, a CCS/CCUS line for an 800 MW coal-fired power plant may need to be able to handle up to 3 million m3 of flue gases emitted by the plant every hour to recover the CO2 from flue gases with CO2 in the range of 3.5 to 14 vol%.⁴

Nonetheless, the right equipment can minimise the costs, material use and energy required for the intensive capture and compression phases. To select effective solutions, businesses should work together with an experienced specialist. More precisely, as separation is at the core of amine-based carbon sequestration processes, it is crucial to identify the mass transfer components that can reliably deliver optimum processing capacity, recovery rates and energy efficiency.

For these activities, columns equipped with structured packing offer the most effective design, as they can maintain a limited equipment footprint, even when high capacity and throughput are required. Furthermore, such a compact solution can still provide the necessary absorption efficiency to remove CO2 from flue gases.

This type of packing minimises pressure drop for a given separation performance. This is of major importance for a system that needs to transport a high-volume flow. A lower pressure drop leads to lower energy consumption in the upstream blower, which finally reduces the Opex and makes the plant less cost intensive. Therefore, businesses can rely on a technology that can maintain low energy consumption and Opex. In addition to this, structured packing features a smaller blower, which helps to reduce Capex. Selecting the right structured packing in CCS/CCUS facilities was shown to save over €225,000 (over $267,000) per year in electricity costs compared to first- or second-generation random packing, providing both environmental and financial benefits.4 Another positive effect of choosing mass transfer solutions with efficiency and low pressure drop is the smaller size of the absorption unit and thus a reduction in Capex.

Ahead of the packing
A structured packing solution that offers all these elements, as it has been specifically developed to address the challenges of carbon sequestration applications, is Sulzer’s MellapakCC. This packing is currently used in several leading CCS/CCUS facilities worldwide, delivering considerable process advantages.

The packing height required to deliver at least the same performance of traditional systems can be 20% smaller. In addition, MellapakCC has been proven to increase efficiency by up to 20%, as well as lowering pressure drop by a minimum of 20% and up to 50-60%.
When applied in a CCS/CCUS facility within an 800 MW coal-fired power plant inputting 3 million m3 of flue gases every hour, MellapakCC can save at least €6.75 million (over $8 million) in Opex over the course of its 30-year service life.³

Beyond separation
By partnering with a mass transfer specialist with extensive experience in separation technology for carbon capture applications, such as Sulzer Chemtech, businesses can benefit from strategies that maximise their return on investment (ROI). This enables companies to benefit from highly effective CCS/CCUS facilities, making decarbonisation an undertaking that can enhance both competitiveness and sustainability.