There are three types of coal power plants currently in use today:
Circulating Fluidized Bed or CFB plants; Pulverised coal-fired (PCF) power plants and Integrated gasification combined cycle (IGCC) plants. All of them produce global warming CO2 and other pollutants.
1. CIRCULATING FLUIDISED BED COMBUSTION (CFB) PLANTS
In CFB, coal is burned with air in a fluid bed mixing gas and solids. This is done either at ambient ("normal" atmospheric) pressure (called Atmospheric CFB) or under pressure (called Pressurized CFB), and at temperatures lower than those in PCF plants. The lower combustion temperatures in CFB systems cut the amount of NOx produced. Finally, because more than 95 percent of sulphur pollutants from the coal can be captured inside the boiler, CFB plants produce less SO2.
However CFB technology is often used with low quality coal. This together with lower thermal efficiencies means that CO2 pollution increases.
CFB uses much lower temperature and less oxygen, resulting in carbon monoxide formation and incomplete breakdown of organic compounds leading to the release of Polycyclic Aromatic Hydrocarbons (PAHs), of which the most potent CANCER-causing agents are: Benzo Anthracene and Benzo Pyrene (USEPA Environmental Document. Dec. 2000. J.L. Jacobson, et al., Journal of Pediatrics 116:38-44. 1990).
Among the pollution problems that the CFB technology does not address are:
1. Coal dust. This is blown to communities during coal transport, and from the coal transfer points, coal crushing station, and uncovered coal piles at coal storage area. Coal dust irritates the lungs. It also accumulates on surfaces of materials (e.g., roofing materials), which causes them to erode.
2. Runoff from coal piles. Created by rainfall, this runoff contains pollutants that contaminate land and water, including municipal water supply sources.
3. Carbon dioxide (C02). This is released during coal burning. C02 is the primary human cause of global warming/climate change, which is causing weather extremes—intense droughts, heavier downpours, floods, and landslides.
4. Small airborne particles. Also released during coal burning, these particulate matters—particularly those with a diameter of less than 2.5 microns—cause grave respiratory ailments such as chronic bronchitis and aggravated asthma.
5. Air toxics. Released either in gaseous or fine particulate form, these toxics include mercury, arsenic, cadmium, other heavy metals, and traces of uranium. These air toxics cause cancer, mental retardation and various disorders of the vital human organs (particularly the lung, kidney and liver) and the nervous system.
6. Polycyclic aromatic hydrocarbon (PAH). Burning of coal at low temperatures results in incomplete breakdown of organic compound and thereby increased PAH emissions, which have carcinogenic properties.
7. Solid wastes (bottom ash and fly ash). CFB coal plants produce more solid wastes than conventional plants because of the limestone used. The coal ash contains toxic substances including arsenic, mercury, chromium and cadmium, which can contaminate drinking water supplies and damage vital human organs and the nervous system. As volumes of coal are reduced to ash, the concentration of these toxic elements increases.
8. Cooling water. Coal plant operations require massive amounts of cooling water. Drawing such water from groundwater sources can deplete local fresh water supplies. When this water is drawn from the sea or other water bodies, fish eggs, fish larvae, and juvenile fish may also come along with it. Moreover, adult fish may become trapped against the intake structures, many of which are injured or die in the process.
9. Cooling water discharge. Being hotter than the water that receives it, this “thermal pollution” has adverse impacts on the aquatic life of the receiving waters. It can decrease fertility and increase heart rates in fish. Coal plants also add chlorine or other toxic chemicals to their cooling water to decrease algae growth. These chemicals are also discharged back into the environment.
2. PULVERIZED COAL-FIRED (PCF) POWER PLANTS
In these plants, coal is ground into a fine powder and blown into a boiler. It burns at between 1,300°C and 1,700°C, creating steam which drives a generator and turbine. This method is by far the most established and common of the three. PCF plants account for over 90 percent of the electricity produced from coal, and about 38 percent of the power generated from any source around the world.
The bad news is that PCF plants are also horribly inefficient. Even the most efficient ones still waste half of their energy and the worldwide average thermal efficiency of PCF plants is less than 32 percent meaning that almost 70 per cent of the energy is wasted. The lower the efficiency level, the more coal needs to be burnt to generate electricity, spewing out even more CO2 emissions.
Ninety percent of the coal fired power stations in the world use this type of technology (Greenpeace).
3. INTEGRATED GASIFICATION COMBINED CYCLE (IGCC) PLANTS
IGCC plants are the newest of the three, with average thermal efficiencies between 40 and 50 percent. At present, the use of IGCC for coal-based electricity production is limited with only four coal-based IGCC demonstration plants in operation globally.
The process they use involves two separate steps: First, coal is turned into gas through a controlled ‘shortage’ of air in an enclosed pressurized reactor. The resulting gas – a mixture of carbon monoxide (CO) and Hydrogen (H2) called Syngas – is then burnt to drive a gas turbine. In the second step, the exhaust gas from step one is used to create steam, which drives a separate steam turbine.
Typically, the gas turbine in step one generates 60 – 70 percent of the power, with the steam turbine generating the rest (Greenpeace).
Local 'cleaner pollutant' defender, like Prof. Danny Piano, who claimed in his letter on SBFCC position and update on coal power plant, “the plant that will be built is based on the new and much cleaner circulating fluidized bed (CFB) technology“, was singing the same out-of-tune song of RP Energy – “clean coal.”
But “clean coal” is a fairy-tale with a devastating ending.
While it is true that some plants are better than others, coal is an inherently dirty fuel. Along with the harm caused by coal mining, global warming CO2 and other pollutants are always produced when it's burnt.