Pre-Combustion vs. Post-Combustion Carbon Capture Technologies

As many are well aware, there is rising advocacy against the effects of fossil fuel-based industrial and residential applications, such as global warming and climate change. Consequently, world leaders and policy-makers are increasingly mandating the incorporation of carbon capture technologies into their industrial processes. These technologies aid the minimization of CO₂ emissions into the atmosphere. In this article, we’ll explore two key carbon capture technologies and identify the advantages and disadvantages of each.

What is Carbon Capture Technology?

Carbon capture technology aims at significantly minimizing carbon dioxide emissions. This technology is particularly essential to the current transition from the fossil fuel-based economy to the innovative sustainable energy era. Carbon capture is a part of the bigger carbon capture, utilization, and storage (CCUS) technology, which is comprised of:

• Capture of CO₂ at large stationary sources (such as coal-fired power plants)
• Utilization of the captured CO₂ in applications (such as gas injection for enhanced oil recovery)
• Feedstock for the petrochemicals
• Transportation of the captured CO₂ to storage sites
• Permanent storage of the CO₂ in the storage site by injection (sequestration).

Two key carbon capture technologies include pre-combustion and post-combustion carbon capture. Keep reading to explore both technologies.

Pre-Combustion and Post Combustion: What’s the Difference?

Several carbon capture technologies are essential for mitigating fossil fuel-related carbon emissions, especially in the power section. Scholars have classified these technologies into pre-consumption capture, oxy-combustion capture, and post-combustion capture. First, let’s identify the key differences between pre-consumption capture and post-consumption capture.

Pre-Combustion Carbon Capture

What is pre-combustion carbon capture? Pre-combustion carbon capture allows the removal of CO₂ from a gas mixture before combustion takes place. Operators typically apply this carbon capture in integrated gasification combined cycle (IGCC) power plants.

The working principle includes partially oxidizing coal in oxygen/air and steam under high temperature and pressure to produce synthetic gas (or syngas). Being a mixture of carbon monoxide (CO), carbon dioxide (CO₂), hydrogen, and smaller portions of other gaseous components, such as methane (CH₄), syngas can undergo the water-gas shift reaction to produce a gaseous mixture significantly comprising H₂ and CO₂. The concentration of CO₂ in this mixture ranges from 15% to 50%. Operators capture, transport, and sequester the CO₂ in the mix, leaving an H₂-rich fuel for combustion.

Benefits and Limitations of Pre-Combustion Capture

Some key benefits of pre-combustion capture include high efficiency and relatively easier carbon removal from fossil fuels. The high CO₂ concentration in the syngas significantly enhances the adsorption efficiency, leading to the formation of a fuel that can be less harmful to the environment. Moreover, researchers have extensively studied the technology, fully developing it for widescale adoption and commercialization. Finally, operators can easily retrofit the technology to existing plants, significantly lowering the cost of adoption.

However, the overall capital cost of the base gasification process exceeds conventional pulverized coal power plants, and the cost of the adsorption processes required to capture CO₂ generated by an IGCC power plant ranges up to $60/tonne. Other key disadvantages of pre-combustion capture include limited IGCC plants, decay issues with utilizing hydrogen-rich fuel, and heat transfer challenges.

Post Combustion Carbon Capture

Post-combustion capture removes CO₂ from flue gas streams after combustion at low pressure. This carbon capture technology is the widely preferred option for retrofitting existing power plants and has been proven to recover CO₂ at a rate up to 800 tonnes/day. Post-combustion capture significantly elevates the energy penalty and transportation and storage costs due to the low concentration of CO₂ in flue gas, ranging from 7 to 14% in cold-fired plants and less than 4% in gas-fired plants. Moreover, the technology exhibits an estimated 70% higher electrical energy production cost due to inefficiencies. Nonetheless, operators are still implementing this carbon technology in their power plant projects.

Benefits and Limitations of Post Combustion Capture

A significant advantage of the post-combustion carbon capture technology is its maturity compared to existing carbon capture alternatives. Due to its existence before World War II, this technology doubles as the most developed of the various carbon capture technologies. This implies that there are standardized techniques for ensuring adequate incorporation of the technology into industrial applications for maintenance if the need arises.

Another benefit is the ease of retrofitting the technology into new and existing plants. Conversely, a major disadvantage of opting for this technology is the low carbon capture efficiency due to low CO₂ concentration in the flue gas. Moreover, the technology is widely associated with large parasitic loads and high electrical energy generation costs.

IFS Can Make CCUS Happen for You

At Integrated Flow Solutions, our world-class expertise in various carbon capture technologies is guaranteed to effectively minimize energy penalties and maximize carbon capture efficiency. Please contact us today for more information about our CCUS technology.