Fly Ash

Waste Manag Res OnlineFirst, published on May 7, 2009 as doi:10.1177/0734242X09103190

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ISSN 0734–242X Waste Management & Research 2009: 00: 1–12

DOI: 10.1177/0734242X09103190

Fly ashes from coal and petroleum cokecombustion: current and innovative potential applications
Aixa González, Rodrigo Navia
Department of Chemical Engineering, University of La Frontera, Temuco, Chile

Natalia Moreno
Department of Geosciences, IDAEA-CSIC, Barcelona, Spain

Coal fly ashes (CFA) are generated in large amounts worldwide. Current combustion technologies allow the burning of fuels with high sulfur content such aspetroleum coke, generating non-CFA, such as petroleum coke fly ash (PCFA), mainly from fluidized bed combustion processes. The disposal of CFA and PCFA fly ashes can have severe impacts in the environment such as a potential groundwater contamination by the leaching of heavy metals and/or particulate matter emissions; making it necessary to treat or reuse them. At present CFA are utilized in severalapplications fields such as cement and concrete production, agriculture and soil stabilization. However, their reuse is restricted by the quality parameters of the end-product or requirements defined by the production process. Therefore, secondary material markets can use a limited amount of CFA, which implies the necessity of new markets for the unused CFA. Some potential future utilization optionsreviewed herein are zeolite synthesis and valuable metals extraction. In comparison to CFA, PCFA are characterized by a high Ca content, suggesting a possible use as neutralizers of acid wastewaters from mining operations, opening a new potential application area for PCFA that could solve contamination problems in emergent and mining countries such as Chile. However, this potential application maybe limited by PCFA heavy metals leaching, mainly V and Ni, which are present in PCFA in high concentrations. Keywords: Coal fly ash, petroleum coke fly ash, reuse, utilization, secondary materials, wmr 08–0090

Introduction
According to the World Energy Council the energy demand has astronomically increased in recent years, and the energy demand is forecast to continue growing at an annualaverage rate of 1.6% between 2004 and 2030 (World Energy Council 2007). This fact, which is based on the current energy mix, implies an increase in the consumption of fossil fuels, of which coal is expected to show the largest demand growth, from about 2772 Mt in 2004 to 4441 Mt in 2030. The two main reasons for this increase are the supply situation for crude oil and natural gas (rising prices,depletion of resources). Therefore, an increase in coal combustion by-products is also expected. The generation of combustion by-products is a global problem with severe implications for human health, environment and industry. On the one hand, high storage, transport and disposal costs must be faced by plant operators and waste management companies and, on the other hand, leaching of elements that areof environmental concern through the soil to the groundwater may impact negatively the terrestrial and aquatic ecosystems (Canty & Everett 2006, Jankowski et al. 2006). Nowadays industry is very interested in the reuse of such by-products as coal (CFA) and petroleum coke fly ashes (PCFA) whenever the reuse allows costs to be saved and to maintain the product quality as well as process stabilityat the same time. Many investigations aim to find new applications for these by-products as raw materials, simultaneously avoiding possible potential risks for the environment and human health, when they are disposed of. Therefore, the main objective of this article is to review current and future applications of CFA and PCFA.

Corresponding author: Prof. Dr. Rodrigo Navia, Department of...