The “pulverized fuel ash” (PFA) or the so-called fly ash (FA), used as a mineral admixture in cement and concrete, is a product of the pulverized coal firing system, through conventional boilers, mostly used in the thermal power plants. While carbon burns in oxidizing surroundings, the inorganic mineral matter gets sintered and liquefied at high temperature. The melt flows down the walls of the furnace and about 25% gets collected as “bottom ash” (BA). It is crushed before disposal. The rest, PFA or FA, gets entrained in the up-flowing hot gas in the form of fine particles, which get trapped in the economizer, air-preheater, mechanical separator, and, finally, battery of electrostatic precipitators (ESP).
As a general practice in many countries, PFA and BA are mixed with water and transported to ash ponds/lagoons. The ash thus deposited in lagoons is called “lagoon ash” (LA) or “pond ash.” It causes problems besides occupying huge stretches of agricultural land. Notwithstanding the greater utilization of PFA (and BA) in recent times in cement and concrete, in bricks, and for land filling, a large quantity of ash still lies unutilized.
As per several estimates, the cement industry contributes about 5% of the global generation of carbon dioxide. The cement industry’s sustainable program developed by the World Business Council for Sustainable Development (WBCSD) prepared an “Agenda for Action” for a 5 year period from 2002 to 2007, endorsed by the leading cement manufacturers of the world. The agenda addressed the issues of (a) climate protection, (b) fuels and raw materials use, and (c) emission reduction besides other issues.
Ref: “Mineral Admixtures in Cement and Concrete”, CRC Press (http://www.crcpress.com/product/isbn/9781439817926). Author: Dr J D Bapat (http://www.drjdbapat.com)
Written for engineers, book focuses on making more workable and durable concrete using mineral admixtures. For each mineral admixture, book looks at manufacturing and processing, physical characteristics, chemical and mineralogical composition, quality control, and reported experiences. It also examines the provisions of national standards.It encourages engineers to more effectively use these and other wastes in cement and concrete to support more sustainable growth of industry. Buy this book online to obtain 20 % discount and free shipping. Download details: http://bit.ly/online_purchase