Clean coal is not a specific type of coal. It combines techniques that reduce pollutants like sulfur and nitrogen oxides and particles. This makes it possible to produce more electricity with less coal (CO 2). Although this would make the coal cleaner, it will take a long time and be costly to store.
Local pollutants can be eliminated.
In the 1980s, the first improvements were made by removing sulfur dioxide from stack gases (SO 2). SO 2 caused acid rain in North America, Europe and North America. This had a devastating effect on forests and influenced public opinion. The treatment of nitrogen oxides, also known as car exhaust, soot, and non-combustible, or particles between 100 and 1 microns, resulted from environmental concerns. These can be eliminated by electrostatic precipitators, cyclone separators, and fabric filters. Researchers are currently focusing on particles less than 1 micron. Treatment of sulfur, nitrogen, and particles can increase the production cost by more than that 20% and, thus, the final cost for electricity.
Increasing power plant efficiency
Another option is to increase power plant efficiency. A plant that produces more energy from the same amount of coal can improve its financial viability and CO fewer pollutants. Traditional power plants have an efficiency of 33%. This means that 67% goes into the atmosphere as CO 2.
The efficiency of new supercritical and ultra-supercritical power plants has increased to 45-46%. This is achieved by raising the temperature to 620°C and the 280/300 bar pressure. The heat is then used to generate additional electricity through cogeneration 1.
The advanced ultra-supercritical power plant is expected to be operational by 2020. It has a temperature range of 700 to 760 degrees Celsius and a 350 to 400 bars pressure range. This will allow for up to half the efficiency. This power plant can produce up to 1100MW. That’s more than traditional nuclear units.
Gasifying coal before it is used in a gas-powered power plant is another efficient way. The efficiency is close to 55%. The process of gasifying coal can also be used to clean it. However, it is expensive because you will need two power plants.
The future of coal will be gasified and sent to fuel cells instead of a gas turbine. Although the expected efficiency of this process is greater than 60%, there are no industrial applications.
Capturing and storing
If it was applied systematically to coal-fired plants, then the capture of CO 2 could be a step in the right direction. However, there are two main obstacles to this:
- It takes large amounts of energy to capture CO 2… The Boundary Dam, Canada’s Saskatchewan province’s only thermal power station capable of carbon capture, uses one-third of its energy to capture CO 2. This decreases the plant’s output from 165 to 110 MW.
- The only way to use captured CO 2 is to re-inject into oil deposits to extract preservation (hydrocarbons). This type of industry has been developed in the United States. However, storing CO 2 at a greater scale below the ground would not be economically feasible if there was a carbon price. This doesn’t take into account transportation problems.
Gas over coal
These techniques may be efficient and effective, but the CO 2 emissions are not as high as replacing coal with natural gas. Natural gas is half the CO 2 of coal and can be substituted for coal to make it more resistant to global warming.
This is true in the United States, where the rise in shale gas production has helped reduce coal for electricity generation and allowed the country to lower its carbon emissions. However, dependence on coal remains strong in large countries like India and China, which are more affordable and have large coal reserves.