In order to protect the environment and reduce carbon dioxide emissions, humans have come up with various methods. Today, Jintong editor will introduce to you the method of capturing carbon dioxide gas. The capture of carbon dioxide is currently considered a mature technology, and compression should not be difficult. However, it still needs to be evaluated and developed for transportation through ships or pipelines, storage in abandoned oil and gas fields or salt formations underground. This is a temporary measure, just a transitional approach before the mature development of low-carbon technology takes shape. Nevertheless, there is still a distance from commercialization, and such large-scale recycling and storage facilities have not yet been seen. The following is a brief introduction to several methods related to chemistry.
Post combustion capture method
The exhaust gas (also known as flue gas) produced after combustion is not only carbon dioxide, but also nitrogen, oxygen, and water vapor, etc. Therefore, it needs to be separated. The common method is to use amine compounds as solvents to absorb carbon dioxide, and then release it through heating. The resulting carbon dioxide is already pure enough and can be stored directly without further treatment. But this approach requires energy consumption, currently consuming approximately 25% of the energy of the power plant, so there are still no large-scale commercial conversion facilities. Other methods include using thin film technology for gas separation, or using solid adsorbents, which require the development of new materials and are still in the research stage. There is another promising new technology, which uses chemical looping, as shown in Figure 2. Firstly, metal powder particles react with oxygen to produce metal oxides, and then the metal oxides are introduced into the combustion chamber. At this time, coal reacts with it, and carbon is oxidized to produce carbon dioxide, while metal oxides are reduced back to metal. Not only is the produced carbon dioxide very pure, but the resulting metal can also be recycled. This method avoids entering air or pure oxygen, indirectly using metal oxides to provide oxygen, thus avoiding the problem of gas purification. If petroleum or natural gas is used, it will not be difficult to separate the generated water vapor. However, this method involves the damage caused by solid metal and metal oxide friction reaction chambers and transportation pipelines, which still requires the design of engineers to overcome. The chemical cycling method utilizes metals to first react with oxygen in the air to form their oxides, which are then introduced into the combustion chamber to undergo redox reactions with coal, producing pure carbon dioxide and recyclable reduced metals.
Pre combustion capture method
This method involves incomplete combustion of coal to produce carbon monoxide and hydrogen gas (known as water gas), followed by a water gas shift reaction between water vapor and carbon monoxide to produce hydrogen and carbon dioxide, which are then removed through adsorption. The remaining hydrogen gas is used as fuel. The challenges faced by this method include the separation of carbon dioxide, reducing the energy consumption of this method, and designing equipment suitable for using hydrogen as fuel, all of which still require research and development.
Oxygen capture method
This method basically requires pure oxygen to be burned with oil or natural gas, and the resulting flue gas still contains too much oxygen, which will be recycled. The advantage is that only carbon dioxide and water vapor will be produced in the end. However, manufacturing pure oxygen is very energy intensive, and the design of the furnace still needs improvement.