Characterization of Magnetic and Non-Magnetic Components From a Low Carbon Fly Ash: A Solid Air Pollutant

Characterization of Magnetic and Non-Magnetic Components From a Low Carbon Fly Ash: A Solid Air Pollutant

Ruma Rano (National Institute of Technology Silchar, India)
DOI: 10.4018/978-1-5225-7289-3.ch002


Low carbon coal ash—a solid air pollutant from super thermal power plant using pulverized fuel combustor—has been characterized in respect of its physico-chemical, mineralogical, and morphological features. Size-classified fractions with their magnetic and non-magnetic components have also been characterized. Low loss on ignition and particle size distribution profile shows fly ash has high utility. The magic number,10 µm, is attained by greater % of particles. The particles with diameter 50 µm occupy population density of 93%. SEM-EDS reveals that particles are mostly globular with high surface enrichment of Al/Si indicating that it will act as un-reactive inert fillers. In magnetic components, various types of Fe bearing phase are present with less porous and more regular shape than non-magnetic components. Finer fractions have high content of magnetite which is expected to help in coal beneficiation. The finer non-magnetic fraction is a source of alumino-siliceous material for synthesizing a novel solid acid or base catalyst for catalyzing industrially important organic reactions.
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Coal – based power plants in India account for about 67% of the total electricity production. Eastern region of the country generates the highest (84%) of the power by coal combustion and in tune, results in huge amounts of fly ash as waste material (Guttikunda and Jawahar,2001). Nearly, 200 million tons of fly ash are produced annually, increasing continuously and estimated to have reached 500 million tons by 2022 (Chatterjee, 2014).

Fly ash is recognized as an environmental pollutant, contains toxic and heavy metals. The ponds where it is usually dumped are poorly managed. Fly ash becomes dry as temperature increases and gets airborne. Thus, it becomes one of the major sources of air and water pollution. Apart from causing various diseases, it also leads to reduction in the recharging of groundwater. Air in areas around coal-fired power plants is polluted with fly ash (Economic times, 2018).Crystalline silica and lime along with toxic chemicals represent exposure risks to human health and the environment. Fly ash contains crystalline silica which is known to cause lung disease, in particular silicosis, if inhaled. Crystalline silica is listed by the IARC and US National Toxicology Program as a known human carcinogen (NTP. Retrieve, 2016) Lime (CaO) reacts with water (H2O) to form calcium hydroxide [Ca(OH)2], giving fly ash a pH somewhere between 10 and 12, a medium to strong base. This can also cause lung damage if present in sufficient quantities. Material Safety Data Sheets recommend a number of safety precautions be taken when handling or working with fly ash (Headwaters Resources. Retrieved,2016). These include wearing protective goggles, respirators and disposable clothing and avoiding agitating the fly ash in order to minimize the amount which becomes airborne.

The literature data revealed that fly ash can be utilized for the removal of NOx, SOx, mercury, and other gaseous pollutants from air and other sources (Ahmaruzzaman, 2012). It can be used as a promising sorbent for the removal of various types of air pollutants; however, further research need to be taken in the laboratory and pilot plant scale. Fly ash also contained approximately 10–12% of unburned carbon and these components have an important role in their removal capacity.

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