Thermal analysis of the products of alkali activation of fly ash from CFB boilers

Abstract

Currently, in the energy sector circulating fluidized bed boilers are popularly used, resulting in the production of large amounts of fly ash. Due to the limited possibilities of utilization, the development of technology for their processing is crucial. One of the most promising and intensively studied ways to exploit fly ash (including those derived from fluidized bed boilers) is their use for the synthesis of zeolite materials. Here, we present the methods of manufacturing zeolite materials from fly ash obtained from hard coal combustion in circulating fluidized bed (CFB) boilers. The paper details the characteristics of the substrates [fly ash from two different combined heat and power (CHP) plants] and products of synthesis conducted according to two methods—the low-temperature method and the fusion method. Both the substrates and the products of each particular synthesis were subjected to thorough examination in terms of density, morphology, phase composition, specific surface area and the average diameter and volume of pores. Conducting thermal analysis combined with quadruple mass spectrometry enabled the interpretation of the physicochemical process occurring during heating and the determination of the thermal stability of the examined materials. Zeolite X was obtained via low-temperature synthesis of fly ash from the CFB boiler of one of the CHP plants. According to the examination, the presence of Ca in fly ash seriously hinders zeolite synthesis.