Carbon/ Post-Combustion Carbon and Capture Technologies

Fossil fuels are still the world’s greatest source of energy and power generation is the largest emitter of carbon in the entire energy sector. In global energy sector, power plants which are fueled by coal and natural gas continue to dominate.

To meet the climate goals, emissions should be addresses transparently and also policy-makers should step and create space for available technology usage and funding. Without the technologies – the best available technologies- such as carbon capture and storage, the emissions cannot be reduced to a point which can be completely beneficial to climate.

Carbon capture and storage is briefly a concept which allows capturing and storing carbon dioxide before it is released to atmosphere. Some technologies can actually capture up to 90% of CO2.

There are three steps to carbon capture and storage (CCS)

1.      Capturing: CO2 separated from other industrial process gases. From industries such as cement and coal and natural gas fired power generation plants.

2.      Transport: CO2 is then compressed and transported via pipelines, road or shipping.

3.      Storage: As final step CO2 is injected into rock formations deep underground for permanent storage.

         Figure 1. Carbon capture in coal fired plant 

       Figure 2. Carbon Capture in Natural Gas Combined Plant 

CCS process was facilitated in Texas/USA as first example in in 1972 and they stored and captured 200million tons of CO2 underground. Although it is a promoted carbon handling technique questions about its safety still on the agenda.

There is also another technique which is Carbon Capture, Utilization and Storage (CCUS), which can be defined as instead of storing the carbon, it re-uses the carbon in other variety of industries as biofuel, plastics or concrete.

In emission control technologies, especially post-combustion capturing / carbon dioxide capturing has a great significance. It refers to capturing CO₂ from a flue gas formed after a combusting reaction happened because of using a carbon based-fuel to generate electricity. Such as coal or natural gas, however, the challenge is real with post-combustion capturing and one of them is separating the relatively low concentration of CO₂ from the large amounts of nitrogen in the flue gas.

In addition, various types of flue gas streams require their own unique carbon capture methods.

Flue gases from natural gas combined cycle (NGCC) plants typically contain ~4% CO₂ by volume (CO₂ concentration of 12-15% in flue gases from coal plants) which provides less driving force for CO₂ separation, and therefore, requires greater energy input – high cost.

There are abundant number of technologies which constantly tries to develop more efficient and also cheaper technologies to create the most efficient capturing technology. It is really important to make it cheaper and efficient since for the mitigation specifically, we need ‘available’ technologies.

Methods usually has solvents which is a method involves chemical or physical absorption of CO₂ from flue gas into a liquid carrier. ,or  sorbents which is a method involves the chemical or physical adsorption of CO₂ using a solid sorbents, or membranes and novel concepts like hybrid systems and cryogenic separation and electrochemical membranes.

These methods are highly susceptible to various factors such as temperature, pressure and the chemical composition used depending on the method used which makes them open to improvement but creates a need for truly meticulous work.

Below, a few of the technologies are indicated. Some of the technologies also can be coupled to increase efficiency. For example,  amine process and biocatalysis can be coupled to increase efficiency. 

Figure 3. Amine Process