The sources and uses of various kinds of chemical gypsum, such as phosphogypsum, fluorogypsum and flue-gas-desulphurisation gypsum, are discussed.
Western Europe produces 23 million tonnes of chemical gypsum per year, 20 million tonnes of which is phosphogypsum. Approximately the same amount of gypsum is consumed, but this is mainly natural gypsum: the total gypsum consumption in Western Europe in 1981 was 25 million tonnes, with phosphogypsum accounting for 2.6 million tonnes.
Natural gypsum is not simply replaceable by phosphogypsum. In the first place, it may not be economic to use phosphogypsum because it has to be purified and dried. In the second place, phosphogypsum can only to a limited extent be used in building products, because it is slightly radioactive. Finally, the fact that phosphogypsum is contaminated with heavy metals, in particular cadmium, on a ppm level, means that disposal, or utilization in roadworks, might require safety measures.
At present, there is no satisfactory method of producing phosphogypsum which is substantially free of Ra and heavy metals. In Western Europe, no more than 10 million tonnes of phosphogypsum per year could be used for traditional applications (building materials, setting retarder for cement). Therefore, if all of the phosphogypsum produced is to be utilized, new products for use in the building industry and in roadworks will have to be developed.
K Weterings, DSM, The Netherlands.
43 pages, 12 figures, 14 tables, 8 references.