A lignite power plant in Germany. Image: r.classen, CC BY-NC-ND 2.0

Carbon capture is an eco-friendly method for ensuring adequate energy supply and allows society to transition to a low-carbon future successfully. The carbon capture technology applies to large-scale emissions processes, such as gas-fired and coal power generation, fertilizer production, natural gas processing, industrial material manufacturing, including iron, steel, cement, pulp, paper and more! Today we will look at existing methods of carbon capture, later in the year I will re-visit this topic to investigate the newest technologies being developed as this article is being written.

Carbon capture and storage or sequestration is an essential carbon dioxide capturing process used for power generation and industrial processes to prevent its emission into the atmosphere. A 2016 research study published in Science Direct Journal highlights that carbon-capturing methods and technologies have a high potential to reduce carbon dioxide emissions into the ecosystem and energy systems.

There are numerous applications of carbon capture methods and technologies, playing a substantial role in reducing the earth’s greenhouse gas emissions. Carbon capture, also known as carbon separation, is widely used in fertilizer and natural gas industries. The question is: What are the best carbon capture methods? In today’s article, we will answer this question. Read on!

Carbon Capture Methods

Energy from fossil fuels, including oil, coal, and natural gas, can result in carbon dioxide emissions as a byproduct. Most coal-based power plants in North America, Europe, Australia, and China use systems that perform coal pulverization into a powder. It is crucial to separate carbon dioxide at diluted concentrations from the combustion flue gases.

Some systems, such as coal gasification that convert coal into chemicals, liquids, and natural gas, allow for easy separation of carbon dioxide. Different methods are used to capture carbon, such as pre-combustion, post-combustion, and oxyfuel combustion systems. Let us now discuss these methods.

Pre-Combustion

Pre-combustion is an effective carbon capture method that converts fuel into gaseous mixtures of hydrogen and carbon dioxide. The power sector uses this method to separate and burn the hydrogen without producing carbon dioxide. The procedure involves compressing the carbon dioxide for transport and storage.

Bear in mind that the fuel conversion steps required for this method are complex than other carbon capture methods, such as post-combustion technology. Therefore, it is often challenging for companies to apply pre-combustion technology to existing power plants. The benefits of the pre-combustion method are a smaller gas volume utilization for carbon dioxide removal.

It is because the process occurs before the dilution of syngas with combustion air, particularly nitrogen. Likewise, the volume flow rate of the target reduces to its higherpressure. The Office of Fossil Energy & Carbon Management reports that pre-combustion carbon capture technology available commercially costs $60 per ton. According to MIT research, the downsides of this method are:

• Existing coal plants show resistance to pre-combustion plant conversion
• The pre-combustion method leads to corrosion issues caused by the syngas
• Unfortunately, existing plants can’t use the pre-combustion technology

Post-Combustion

Post-combustion focuses on separating carbon dioxide from combustion gases. The method involves using a liquid solvent to capture carbon. That’s why the post-combustion method is also known as the absorption-based approach, involving carbon dioxide absorption by the solvent and releasing it by heating to form a purity CO2 system.

The food and beverage industry widely uses this method to capture CO2. The primary advantage of post-combustion carbon capture is that plants can use existing combustion technology and retrofit to existing plants is possible.

However, the energy penalty of this method is relatively higher than other methods. The good news is that advanced process developments can reduce the energy penalty. Moreover, oxygen and impurities can degrade solvents, requiring the power plants to dispose of the degraded solvent.

According to AICHE, new coal-based power plants have a limit of 1,100 pounds per hour for carbon dioxide emission. That way, coal-fired power plants can reduce 50% of emission levels. According to the Department of Energy, the cost of carbon capture using the post-combustion method will reach $40 per ton by 2025.

Oxy-Fuel Combustion

Oxyfuel combustion is a sophisticated carbon capture method that uses oxygen instead of air for fuel combustion. The purpose is to produce exhaust gas that contains CO2 and water vapors, leading to easy separation of these compounds to create a high purity carbon dioxide stream.

Bear in mind that oxyfuel combustion is an integral part of carbon capture and storage. It involves burning the fuel with pure oxygen and recycling the flue gas into the boiler or furnace to control the flame temperature.

Typical applications of oxyfuel combustion processes are the glass industry, thermal energy engineering, and metallurgical industry. A growing body of research evidence shows thatoxyfuel is highly efficient, reliable, and energy-saving technology,unlike pre-combustion and post-combustion methods. The primary benefits of using this method are:

• Production of highly concentrated CO2 stream for capture and storage
• Reduced flue gas flow that leads to integrated emissions control
• Reduction of combustor unit volume and size to 20%,unlike air-fired combustion

Although oxyfuel technology is highly efficient, it has higher investment costs than other methods. Another downside of this method is a complex plant with reduced or low up-time. Using this method also requires companies to develop H2 turbines that can cost a lot of money.

In addition, separating large volumes of air into argon, gaseous nitrogen, liquid oxygen, and other trace gases is challenging for companies using oxyfuel systems. The oxyfuel system can use 15% or more power produced at the power station.

Final Words

Carbon capture and storage offer a wide range of benefits, primarily reducing carbon dioxide emissions into the atmosphere. Not only do carbon capture methods protect human health and other species in the ecosystem, but it also reduces global warming and combat climate change.

Carbon capture is a safe and reliable technology that captures and transport carbon dioxide to the earth’s surface for storage purpose. Lower emission rates of CO2 in the atmosphere will make the planet a comfortable place.

Otherwise, global warming and climate change are causing significant damage to it. Governments worldwide, especially advanced countries like the U.S, Canada, France, Germany, Australia, England, and others, are making substantial efforts to streamline the carbon capture technology and launch new/effective methods. Which as mentioned we will investigate later this year!

Thanks for reading,

Daniel Biocchi