Carbon Capture Begins : An Analysis Of Pre-Combustion Carbon Capture Storage (CCS)
CO2 emissions related to Anthropogenic energy are increasing everyday. Although the countries have pledged to decrease their fossil fuel based emissions, still there are many fossil fuel power generation stations and vehicles introduced to the consumer. Therefore, in addition to moving away from fossil fuel sources there is a need to implement methods to capture the emissions to keep the harm mitigated. In the first article of this series we briefly introduced the concept of CCS and its role in reducing the global CO2 emissions.
The International Energy Agency (IEA) Blue Map scenario targets CCS to reduce CO2 additions by 19% by the year 2050. This will mean capturing around 8 Gt of CO2 per year by the time. These targets will be faced with great challenges with the increased urbanization and increased energy consumption per capita,
First, let’s look at how the CO2 is formed in the industrial processes. CO2 is formed in the combustion of Carbon based compounds with Oxygen presence. There are several combustion processes used in the industry. The CO2 removal process also depends on the type of combustion process used in the application. Therefore, unique designs of CCS systems are expected based on the type and the scale of the system which results in high costs.
CCS systems identified with the combustion process are of three main types. Pre-combustion, post-combustion and oxyfuel combustion are the three types. In this segment we look into the pre-combustion CCS.
Pre-combustion process reduces the potential sources of CO2 from the participating fuels before the combustion/ energy conversion occurs. The participating fuels are usually coal or natural gas. Coal is still a significantly consumed energy source*. Natural gas has been considered a transitional fuel that has allowed the dependence on fossil-fuels like coal and oil to reduce during last couple of decades. In 2017, 14% of Europe’s primary energy production was based on natural gas**. Eurasia and Middle East regions still remains to be significant consumers of natural gas contributing to considerable amount of CO2 emissions from natural gas.
To reduce the potential sources of CO2, a pretreatment of fuel is required. For coal, fuel is first converted to CO and H2 using a gasification process. This result is known as the syngas. Then through a water-gas shift mechanism the CO is further converted to CO2 and H2. The CO2 is captured at this point. For CH4, the fuel is converted to syngas through a reform process. Therefore, the compound burned as the fuel at the end is H2 in which the product is energy and water vapor. Water vapor can also be condensed. Studies show up to 80% CO2 capture efficiency is a possibility in pre-combustion CO2 capture systems.
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*Scott, V., Gilfillan, S., Markusson, N., Chalmers, H. and Haszeldine, R.S., 2013. Last chance for carbon capture and storage. Nature Climate Change, 3(2), p.105.
**http://ec.europa.eu/eurostat/statistics-explained/index.php/Energy_production_and_imports#Further_Eurostat_information
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