FGD gypsum as raw material used in the gypsum industry Variations in quality and quality problems, impact on the product, elimination of malfunction in the flue gas desulphurisation system (FGD)

摘要

As early as at the end of the 1970s, the Knauf subsidiary Knauf Research Cottrell developed, in close co-operation with the electricity industry, a two-stage desulphurisation process for the production of utilisable flue gas desulphurisation (FGD) gypsum. Since the ordinance for large combustion plants has come into force in 1983, this process stands for one of the leading desulphurisation processes around the globe. Process development not focused on the compliance with the given emission limits, but also on the production of the by-product FGD gypsum having a specification which ensured the substitution of natural gypsum with respect to the production of gypsum-based building materials and gypsum-based building products. In the meantime, more than 10 million tonnes of FGD gypsum per annum are being produced (in 2007, 15 member states of the EU). More than 7 million tonnes of the total quantity are produced in Germany alone with a utilisation rate of nearly 100%. The major quantity of the FGD gypsum produced is used in the gypsum industry for partial substitution of natural gypsum. A smaller quantity is used as setting retarding agent in the cement industry. This paper gives an overview about the most important specification parameters to be observed, the product status of FGD gypsum and the process steps in the gypsum industry for the further processing of FGD gypsum as well as the significant process steps and possible malfunction sources during the production of FGD gypsum in wet desulphurisation processes.