Calcium sulfate, conversion

Formation of emissions from fluidised-bed combustion is considerably different from that associated with grate-fired systems. Flyash generation is a design parameter, and typically >90% of all soHds are removed from the system as flyash. SO2 and HCl are controlled by reactions with calcium in the bed, where the lime-stone fed to the bed first calcines to CaO and CO2, and then the lime reacts with sulfur dioxide and oxygen, or with hydrogen chloride, to form calcium sulfate and calcium chloride, respectively. SO2 and HCl capture rates of 70—90% are readily achieved with fluidi2ed beds. The limestone in the bed plus the very low combustion temperatures inhibit conversion of fuel N to NO. ... 

Naphthalenesulfonic Acid. The sulfonation of naphthalene with excess 96 wt % sulfuric acid at < 80°C gives > 85 wt % 1-naphthalenesulfonic acid (a-acid) the balance is mainly the 2-isomer (P-acid). An older German commercial process is based on the reaction of naphthalene with 96 wt % sulfuric acid at 20—50°C (13). The product can be used unpurifted to make dyestuff intermediates by nitration or can be sulfonated further. The sodium salt of 1-naphthalenesulfonic acid is required, for example, for the conversion of 1-naphthalenol (1-naphthol) by caustic fusion. In this case, the excess sulfuric acid first is separated by the addition of lime and is filtered to remove the insoluble calcium sulfate the filtrate is treated with sodium carbonate to precipitate calcium carbonate and leave the sodium l-naphthalenesulfonate/7J(9-/4-J7 in solution. The dry salt then is recovered, typically, by spray-drying the solution. 

ChemicalRecope . There are advantages and disadvantages to each of the base systems employed in sulfite pulping (see Table 4). Each has its own potential recovery systems except the calcium system, which is obsolete. Calcium-based Hquors can be burned, but scaling problems are severe, and conversion of the calcium sulfate to CaO is not economical. 

Conversion of the permanent, noncarbonate hardness salts such as calcium sulfate or chloride produces more insoluble calcium carbonate using soda ash. The total noncarbonate hardness is the sum of the calcium sulfate or chloride present in the original RW plus that formed from magnesium sulfate or chloride in the previous reaction. 

CALCIUM SULFATE. CAS. 10101 -1 1-4], Calcium sulfate, CaSOj. in mineral form is commonly called and occurs abundantly in many areas of the world. In natural deposits, the main form is the dihydrale. Some anhydrite is also present in most areas, although to a lesser extent. Mineral composition can be found in Table 1. The hemihydrate is normally produced by heal conversion of the dihydrale from which HiO is removed as vapor. The resulting powder is also known as plaster of Paris. Stucco has the greatest commercial significance of these materials. It is the primary constituent used to fabricate products and in formulated plasiers used in job or shop-site applications. 

L-Malic acid (HOOC CH2 CHOH COOH) for use in the pharmaceutical industry is manufactured by conversion of fumaric acid by the intracellular enzyme fumarase produced by various microorganisms. The excess fumaric acid is easily separated by crystallization after concentration of the mother solution. Further addition of lime allows malic acid to be separated as calcium malate within a bioreactor crystallizer system. By adding diluted sulfuric or oxalic acid, the salt is split into free malic acid and calcium sulfate or oxalate, the latter being removed by filtration (Mourgues et al., 1997). 

The sulfur sorbent that has received the most attention is limestone because of its widespread availability and low cost. Unfortunately the conversion of limestone to calcium sulfate results in a volumetric increase, and it can be readily shown (8 ) that for particles that do not permit volumetric expansion on reaction the maximum conversion attainable is about 59 percent (the value is dependent on the specific volumes of reactant and product). This constraint can be avoided by use of dolomite, since the MgO is not sulfated and the void volume produced by the decomposition of MgCO and CaCO is sufficient to permit complete calcium utilization, but at the expense of an added weight of sorbent and added energy requirement for calcination. The above conclusions follow from consideration of the stoichiometric relations ... 

AIPO4 is isoelectronic with silica and, as such, readily forms glasses and Si02-like crystalline materials. As well, framework stmctmes similar to zeolites may be prepared by the use of amines as templates. Like zeolites, these are active in catalytic reactions such as methanol conversion to hydrocarbons (seeZeolites) As a ceramic material, AIPO4 is an infusible material that is insoluble in water but is soluble in alkali hydroxides. It is often used with calcium sulfate and sodium silicate for dental cements. AIPO4 is also used as a white pigment that also acts as a corrosion inhibitor. 

Sulfuric acid and sodium hexametaphosphate (SHMP) are injected in the feedwater line upstream of the cartridge filters. The sulfuric acid is injected to adjust the feedwater pH to a level of between 4 and 6. The purpose of acid injection is twofold. The primary purpose is to mitigate the possibility of calcium carbonate deposition by conversion of bicarbonate to carbon dioxide. Coincidentally, the rejection performance of the thin film composite membrane is pH sensitive and the optimum performance is at the operating pH level. SHMP is added to the feedwater as a threshold inhibitor to inhibit the crystalline growth of sparingly soluble salts such as calcium sulfate. 

More recently, calcium sulfate was applied to the dehydration of glycols into unsaturated carbonyls 31), cupric sulfate mounted on alumina was used for the conversion of aUyl ether to allyl alcohol 32), and some metal sulfates were used for the open-chain polymerization of ethylene oxide 33). 

Let us consider the homogeneous reaction of iron (II) ions with permanganate ions in an acidic solution as well as a heterogeneous reaction of dissolving calcium sulfate in water. For clarity, we will omit the chemical terms and insert only the electric ones below the substances into the conversion formula ... 

After the free calcium sulfate has been consumed, the AFt phase that was formed in the earlier stages of hydration reacts with non-reacted CjA and C2(A,F) and converts to AFm. This conversion may or may not pro-ceed to full completion, and some AFt may still be present even in fully hydrated pastes. 

In cements in which the calcium sulfate content has been too low for complete conversion of all the AI2O3 present in the original cement to ettringite, a formation of the AFm phase may get under way in a reaction between ettringite and AH3, after all the calcium sulfate has been used up ... 

Quantification of Calcium Sulfate Phase Transformations In order to quantitatively describe the progress of phase conversion ratios of absolute intensities of characteristic peaks of each phase s XRD pattern were compared. This method is generally considered suitable for quantitative phase analysis of mixtures [35]. To aid phase quantification, calibration curves based on prepared mixtures with known composition were used and the respective intensity ratios calculated. The intensity ratios were calculated from the intensity of peaks at 26 29.10725.43°, 29.71°/25.43° and... 

This reaction under similar conditions can go one step further to anhydrous calcium sulfate, hence the calcination temperature must be carefully controlled for complete conversion to the hemi-hydrate. 

The manufacturing process for citric acid involves fermentation followed by downstream purification. A common method of purification is to treat the products of fermentation with lime slurry followed by reaction of the solid calcium citrate formed with aqueous sulfuric acid to give an aqueous solution of pure citric acid and a precipitate of calcium sulfate. Note that the final purification step represents a system in which a sparingly soluble solid (calcium citrate) reacts with a liquid product (citric acid) and a solid precipitate (calcium sulfate). Experimental data of Anderson et al. (1998) plotted as conversion versus time showed a sudden rise in conversion at 85%, the exact point at which precipitation started. This clearly suggests autocatalytic action by the precipitating solid. 

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