Gypsum, synthetic

Fig. 8.22 Roller press for the briquetting of (synthetic, FCD) gypsum in a flue gas desulfurization plant inset, synthetic gypsum briquettes (courtesy Kdppern, Hattingen/Ruhr, Germany)...

FGD material Wallboard, stabilized road base/subbase, structural fill, surface mine reclamation, underground mine injection, livestock pad, low permeability liner, synthetic gypsum raw material, liming substitute, soil conditioning, synthetic aggregate, sludge stabilization... 

Other systems control the coal burn to minimize emissions of sulfur dioxide, nitrogen oxides, and particulates (Darcovkic et al., 1997 Bhanarkar et al., 2008). Wet scrubbers, or flue gas desulfurization (FGD) systems (Table 22.3), remove sulfur dioxide, a major cause of acid rain, by spraying flue gas with limestone and water. The mixture reacts with the sulfur dioxide to form synthetic gypsum, a component of drywall. 

Potgieter, J. H., Potgieter, S. S. Mccrindle, R. I. (2004). A comparison of the perfoimance of various synthetic gypsums in plant trials during the manufacturing of OPC clinker. Cement Concrete Research 34, 2245-2250. 

Several studies have demonstrated that mercury can be captured in these systems but only mercury oxidized is soluble in water [58-59]. Depending on the FGD process a portion of this mercury may be incorporated into the FGD slurry and its solid by-products including synthetic gypsum. 

In 2008, 159 Mt of gypsum was produced by mining worldwide. A second source referred to as synthetic gypsum is produced in the flue gas desulfurization processes described in Box 12.2. The contribution made by synthetic gypsum to world supplies is growing in importance, and its production is... 

Strydom, C. A., D. L. Hudson-Lamb, J. H. Potgieter and E. Dagg (1995). The thermal dehydration of synthetic gypsum . Thermochimica Acta 269-270 631-638. 

Soil conditioners are materials that measurably improve the physical characteristics of the soil as a plant growth medium. Typical uses include erosion control, prevention of surface sealing, and improvement of water infiltration and drainage. Many natural materials such as peat and gypsum are used alone or in combination with synthetics for soil conditioning. This article is concerned with synthetic soil conditioners, many of which are introduced as polymeric systems similar to the gels and foams formed in situ by chemical grouts. 

This article discusses traditional hull ding and construction products, ie, not made from synthetic polymers (see Building materials, plastic), including wood, asphalt, gypsum, glass products, Pordand cement, and bricks. The article presents information about each basic material, the products made from it, the basic processes by which the products or materials are produced, estimates of the quantity or doUar value of the quantities produced or used in the United States, and some pertinent chemical or physical properties related to the material. More detailed chemical and physical property data can be found in articles devoted to the individual materials (see Asphalt Cement Glass Wood). 

Ammonium sulphate is increasingly produced by reaction of synthetic ammonia with sulphuric acid from the process for production of caprolactam and via a method using gypsum. Ammonium sulphate is also used as a fertilizer. 

To size the two species however, it is necessary to separate them. A sink-float technique has been developed to separate the two. A carbon tetrachloride - tetrabromoethane mixture having an SG about 2.5 was used. The dry crystal mixture is added to the dense organic liquid, then put under vacuum to remove entrapped air bubbles. The suspension is then centrifuged for several hours to separate out the gypsum which floats and the hemihydrate which sinks. Tests on synthetic mixtures showed that a very clean separation is possible. 

Pneumatic conveyor dryers yeast filter cake, starch, whey, sewage sludge, gypsum, fruit pulp, copper sulfate, clay, chrome green, synthetic casein, and potassium sulfate... 

Not all mine drainage or natural runoff from rock outcrops are acidic, even when extensive sulfide oxidation is present. Synthetic cyanide solutions, which are often used to extract gold and other metals from ores, can greatly increase the alkalinity of mining wastes and neutralize sulfuric acid (Craw et al., 1999). In other cases, the sulfuric acid is effectively neutralized by alkaline soils, limestones, dolostones, marbles, shams, or other carbonate-rich rocks (Pfeifer et al., 2004, 219 Razo et al., 2004 Lee, Lee and Lee, 2001, 491 Mendoza et al., 2006). Reactions between calcium carbonate and sulfuric acid may precipitate gypsum (CaS04 2H20). 

Mixed waste paper can also be utilized for uses other than paper. The uses include (1) molding of paper fibers mixed with PE or polypropylene to form door panels, trunk liners, and plastic lumber (2) nonwoven mats of up to 90% paper fibers held together by synthetic fibers and (3) composites of wood, paper fiber, and gypsum. 

Wood-based panel products are usually bonded with synthetic adhesives based on condensates of phenol, resorcinol, urea, or melamine with formaldehyde. Particleboards and fiberboards can also be bonded with mineral binders like cement or gypsum. Wood adhesives derived from natural products have more... 

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