Accelerated Carbonation of Coal Combustion Fly Ash for Atmospheric Carbon dioxide Sequestration and Soil Amendment: An Overview

摘要

Fly ash is one of the major solid by-products generated by coal combustion for power generation. At present most fly ash generated all over the world is dumped as waste material without any beneficial use. Only a small proportion of the total fly ash production is used in applications such as cement production, mineral wool production, recovery of metals, road sub-base construction, mine reclamation, and in agriculture. In addition, fly ash is a material that can be used to capture and store atmospheric CO2 through mineral carbonation both in situ and ex situ of the source of CO2 emissions. As a means of increasing the rate of mineral carbonation, accelerated carbonation has been researched by scientists in the recent past. In addition to achieving the benefits of carbon sequestration, accelerated carbonation can make the fly ash chemically stable, which is beneficial in overcoming problems associated with the leaching of toxic elements when using it as a soil amendment. Therefore, through accelerated carbonation followed by addition to soil this solid waste material can be successfully managed. The efficacy of the mineralization reaction depends on the mineralogy, and the physical and chemical properties of fly ash and the reaction conditions, such as CO2 partial pressure, temperature, relative humidity and the contact time of gas and the material. In order to achieve higher CO2 sequestration efficiency it is vital to select material with the required properties and to supply it with the optimum reaction conditions. This paper reviews the main issues related to the accelerated carbonation of coal combustion fly ash under different reaction conditions and its effects on CO2 sequestration efficiency. It also identifies the potential application of carbonated fly ash to soil in order to improve soil’s physical and chemical properties.