Fly Ash Bricks-Waste Management in Thermal Power Plants
Coal-based thermal power plants produce wastes in multiple forms. The combustion of coal produces a host of gases that are unsuitable for the natural atmosphere, and it leaves behind ash after the complete burning. There are catalytic converters and sensors which detect and regulate the amount of oxides of sulfur and nitrogen along with other harmful substances. Ash, on the other hand, is harder to manage as by it is a tangible waste and is quite harmful in nature.
Traditional practices and current practice in America involve storing ash in specially sealed concrete containers and in specially designated ash dumps and ash dikes. This method is inefficient and consumes a lot of resources and space. Added to this, the system is not safe from an environmental point of view. Ash sludge and ash, in general, can easily seep into the ground or get dissipated in the air. One of the most effective ways of dealing with ash waste that is quite popular in Europe and certain Asian countries involve the manufacturing of fly ash bricks.
What are fly ash bricks?
Fly ash bricks are a variety of typical masonry bricks that are made out of C class and F class ash and water. Typical ash from thermal power plants is treated in multiple steps to create long-lasting bricks that last for more than 100 freeze and thaw cycles. The ash is first pulverized completely and compressed at about 270 atm. It is then cured for 24 hours at 66 deg. Celsius in a steam bath. Finally, the bricks are strengthened using an air entrainment agent. These fly ash bricks are often termed as self-cementing bricks due to the high percentage of calcium oxide. The presence of high calcium oxide mainly comes from C class ash.
Compared to traditional clay brick manufacturing techniques, manufacturing of fly ash bricks cause less mercury pollution, are energy efficient and cost about 20% lesser than typical clay bricks. Additional developments continue to take place in the field of fly ash manufacturing that reduces its cost of manufacturing and improve its properties. For example, the technique of creating fly-ash lime gypsum, also known as FaL-G revolutionized the world of fly ash bricks. Simply by adding gypsum to fly ash and a mixture of lime, the calcium aluminates were converted into calcium alumino-sulfates which drastically improved its strength. FaL-G bricks do not need any kind of pressure, and the curing takes place at ambient temperatures of 20 to 40 deg. Celsius.
Fly ash is the major pollutant from coal-based thermal power plants. Due to the particulate nature of the pollutant, it is extremely dangerous and harmful for the environment. Making masonry bricks out of fly ash is one of the most ideal solutions to the problem of managing this waste.