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Chemicals from Non-hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Sulfur reacts directly with methane to give carbon disulfide (CS2) which is used to manufacture cellophane and rayon. One of the uses of elemental sulfur is in vulcanization of rubber, where polysulfide chains cross-link organic polymers. Large quantities of sulfite derivatives are used to bleach paper and to preserve dried fruit. Many surfactants and detergents are sulfate derivatives. Calcium sulfate (gypsum, CaSO4 2H2O) is used in Portland cement and in fertilizers. The most important form of sulfur for fertilizer is the mineral calcium sulfate.
Dissolved Matter
Published in Paul N. Cheremisinoff, Handbook of Water and Wastewater Treatment Technology, 2019
Calcium sulfate is the only scale-forming salt in the noncarbonate hardness for magnesium sulfate, and the chlorides and nitrates of both calcium and magnesium have solubilities exceeding 150,000 ppm by weight expressed as CaCO3, even at 32°F and over 356,000 ppm at 12°F. Calcium sulfate, in the form of gypsum, has a solubility curve which, on elevations of temperature, shows a rise up to about 104°F after which it falls until, at 212°F, it is slightly below the solubility at 32°F. At boiler temperatures the curve falls rapidly, until at 322 psi it is only some 40 ppm, expressed as calcium carbonate. Table 4 shows calcium sulfate solubilities.
Effect of gypsum and cement content on unconfined compressive strength of soft sediment
Published in International Journal of Geotechnical Engineering, 2021
Masoud Janbaz, Lauren Iacobucci, Kelly Francisco, Robert Miskewitz, Masaki Kitazume, Ali Maher
Calcium sulphate is an inorganic compound with the chemical formula CaSO4. The typical composition of Portland cement includes some gypsum, used to hinder the rate of hydration of calcium aluminate minerals. The hydration of calcium aluminates in water results in the production of hydrogarnet and the generation of a significant amount of heat (Thomas and Jennings 2009). The presence of gypsum can obstruct this reaction and avoid premature ‘flash setting’ of cement paste under high heat (Thomas and Jennings 2009). An increased ratio of gypsum to calcium aluminates in the cement mixture can greatly influence the types of hydration products formed. Some research has been conducted on the use of gypsum as a binding agent to improve the quality of fine-grained soils for use as construction materials (Salas et al. 1973; Petrukhin and Arakelyan 1984). Gypsum can improve the friction angle (ϕ) of clays (Salas et al. 1973), the California Bearing Ratio (CBR) of silty clays (Al-Ani et al. 1988), and compressive strength of sandy soils (Ahmed, Ugai, and Kamei 2011). A range of gypsum contents (between 3% and 20%) has been assessed, and it is generally concluded that the addition of gypsum will increase the structural rigidity of test samples. According to Petrukhin and Arakelyan (1984), the addition of 15% gypsum to clayey soil sharply increases the specific cohesion. This is believed to result from the formation of crystals in pore spaces of the soil, overall reducing porosity and increasing the soil rigidity. Gypsum can also change the hydraulic conductivity of soils (Subhi 1987; Al-Dabbagh et al. 1990) and reduce the swelling potential of expansive clays (Ameta, Purohit, and Wayal 2007, Yilmaz and Civelekoglu 2009).
Investigation of Crystallization Fouling on Novel Polymer Composite Heat Exchanger Tubes
Published in Heat Transfer Engineering, 2022
Sebastian Schilling, Heike Glade, Thomas Orth
Major crystal modifications of calcium sulfate are dihydrate (gypsum, CaSO4·2H2O), hemihydrate (CaSO4·½H2O), and anhydrite (CaSO4). Hemihydrate has a higher solubility and becomes important at higher temperatures which are not considered here.