Phosphogypsum Production

Thirteen core samples were used from the earlier study of the environmental impact of phosphogypsum production (/). The sample identifications are the same as in that work A through I each represents an individual stockpile, and 1,2, and 3 represent different cores on the same stockpile. Five additional core samples were obtained for this study. The new samples were taken only through a short section approximately 3 m above and 3 m below the interface with the ground surface. The samples contained phosphogypsum or soil. The sample identifications are the same as before A, B, F, and H refer to the same stockpile as in Ref / 1 and 2 refer to different cores on the same stockpile, but the samples are differentiated from the former samples by -2, for example, F2-2. All sample depths are measured from the tops of the stockpiles of phosphogypsum. 

Phosphogypsum [13397-24-5] is the name given to the by-product gypsum residue when phosphate ore is acidulated to extract phosphoric acid. There are several processes commercially used. AH of them digest or acidulate tri-calcium phosphate. 

Miiller-Kiihne A process for recovering sulfuric acid from phosphogypsum, the waste product from the manufacture of phosphoric acid. The process is economic only if the lime co-product is converted to cement. Based on the work of W. S. Muller and H. H. Kiihne at Bayer, Leverkusen, from 1915 to 1918. Further developed in Germany in the 1950s and still in operation in Germany and Austria in 1989. 

In a recent document [25] presenting techniques adopted by the French for pollution prevention, a new process modification for steam segregation and recycle in phosphoric acid production is described. As shown in Figure 9, raw water from the sludge/fluorine separation system is recycled to the heat-exchange system of the sulfuric acid dilution unit and the wastewater used in plaster manufacture. Furthermore, decanted supernatant from the phosphogypsum deposit pond is recycled for treatment in the water filtration unit. The claim was that this process modification permits an important reduction in pollution by... 

Coupled with the energy consumption is the environmental effect from production of these binders. For every ton of phosphoric acid, 5 ton of phosphogypsum (calcium sulfate) is produced [15]. This waste can be recycled into value-added products such as gypsum board, but often there is a radioactivity issue. Some phosphogypsum contains radium and emanates radon gas. At the present time, such waste can only be disposed in a landfill. 

Bhattacharya, A. 1976. Production of Sulphuric Acid and cement from Phosphogypsum Using OSW Process, Chem. Age India 27, 1009- 1014. 

The largest quantity of byproduct gypsum arises in the production of phosphoric acid (so-called phosphogypsum ) by the reaction of natural phosphates with sulfuric acid (see Section 1.5.1) ... 

The impurity content can be affected by the way in which the phosphoric acid manufacturing process is carried out single stage processes, or newer processes, which lead to the hemihydrate, have a higher impurity level, so that further purification steps are necessary. Two step processes, which either lead via the dihydrate to the hemihydrate (Central-Prayon process) or via the memihydrate to the dihydrate (Nissan process), provide products, which can be utilized without further purification steps. Should further purification of the phosphogypsum be necessary, two types of process are possible ... 

H. El-Shall, E.A. Abdel-Aal, and B.M. Moudgil, Effect of Surfactants on Phosphogypsum Crystallization and Filtration... During Wet-process Phosphoric Acid Production, Sep. Set. Technol. 35(3), 395 10 (2000). 

It has been previously stated here that U.S. desulfogypsum production by 1990 might be as much a.s 30 to 35 million metric tons per year, about the same as phosphogypsum for the same year. Referring back to Fig. 2, there is a striking similarity to the projected U.S. BPG supply position in 1990, and Japan s comparable BPG supply relationship in 1982. Here the comparison stops because Japan is recycling substantially all of the BPG for the traditional uses as indicated in Fig. 3, and the United States has no firm plans to develop similar u.ses by 1990. 

Getting Rid of Phosphogypsum—ill. Conversion to Plaster and Plaster Products, Phosphorus and Potassium. No. 94, March/April 1978, pp. 24-39. 

KEY WORDS gypsum, phosphoric acid, radium, bypnxiuct gypsum, phosphogypsum, hazardous waste, phosphate fertilizer production... 

In 1978, U.S. production of crude natural gypsum was estimated at 13.5 million metric tons. Annual domestic gypsum consumption in 1978 was at 22.1 million metric tons (/], of which 635 000 metric tons were phosphogypsum. 

Phosphogypsum is the major byproduct of wet-process phosphoric acid production. Phosphate rock, which is composed of apatite minerals (4], (calcium phosphates containing varying amounts of carbonate and fluoride), is digested with sulfuric acid and water to produce phosphoric acid, phosphogypsum, and minor quantities of hydrofluoric acid. 

Agglomeration of finely divided gypsum, such as phosphogypsum or flue gas gypsum, into a lumpy product can be done by any one of the following processes ... 

Rutherford PM, Dudas MJ, Arocena JM. 1996. Heterogeneous distribution of radionuclides, barium and strontium in phosphogypsum by-product. Sci Total Environ 180 201-209. 

Fluorogypsum and phosphogypsum are sulfate-rich by-products generated during the production of hydrofluoric and phosphoric acid, respectively. Full descriptions of these wastes [196-206] are given in Table 10. 

Phosphogypsum - Phosphogypsum is a solid by-product of phosphoric acid production... 

Sulfuric acid is added to the slurry to produce phosphoric acid (H3PO4) and a phosphogypsum (hydrated calcium sulfate) by-product... 

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