Calcium-based

Petroleum. Apart from its use ia petrochemicals manufacture, there are a number of small, scattered uses of lime ia petroleum (qv) production. These are ia making red lime (drilling) muds, calcium-based lubricating grease, neutralization of organic sulfur compounds and waste acid effluents, water treatment ia water flooding (secondary oil recovery), and use of lime and pozzolans for cementing very deep oil wells. 

Wood Pulping. The system Mg(OH)2 S02 H20 is also used in acid bisulfite pulping. Compared to a calcium-based system which is not as amenable to regeneration of the pulping bisulfite (87), fewer technical problems are encountered in the digesters, evaporators, or recovery boiler of the Mg-based process. In the presence of excess SO2, bisulfite forms in a 43% MgSO solution, at 25°C and 101.3 kPa (1 atm) SO2 pressure, to increase MgSO solubihty. 

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 Each has its own potential recovery systems except the calcium system, which is obsolete.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. 

Many other recovery alternatives have been proposed that iaclude ion exchange (qv), pyrolysis, and wet combustion. However, these have not gained general acceptance. A limited number of calcium-based mills are able to utilize their spent pulpiag liquors to produce by-products such as lignosulfates for oil-weU drilling muds, vanillin, yeast, and ethyl alcohol (see PETROLEUM Vanillin). 

Calcium Chelates (Salicylates). Several successhil dental cements which use the formation of a calcium chelate system (96) were developed based on the reaction of calcium hydroxide [1305-62-0] and various phenohc esters of sahcyhc acid [69-72-7]. The calcium sahcylate [824-35-1] system offers certain advantages over the more widely used zinc oxide—eugenol system. These products are completely bland, antibacterial (97), facihtate the formation of reparative dentin, and do not retard the free-radical polymerization reaction of acryhc monomer systems. The principal deficiencies of this type of cement are its relatively high solubihty, relatively low strength, and low modulus. Less soluble and higher strength calcium-based cements based on dimer and trimer acid have been reported (82). 

Components in the invading water-based filtrate and in the formation waters may react to form insoluble precipitates which can block the pores and give rise to skin damage. The scale can be formed by interaction of calcium-based brines with carbon dioxide or sulfate ions in the formation water. Alternatively sulfate ions in the invading fluid may react with calcium or barium ions in the formation water. Analysis of the formation water can identify whether such a problem may arise. 

In an attempt to combine the syndioselectivity of half-sandwich titanium catalysts with the living characteristics of anionic polymerization initiators, the use of half-sandwich calcium-based catalysts has been described.363 364 In neat styrene complex (152) affords 76% rr triad PS. However, polydispersities are still quite high (Mw/Mn > 2.2)... 

Gupta, H., M. Iyer, B. Sakadjian, and L.S. Fan, Separation of COz from flue gas by high reactivity calcium-based sorbents, Pittsburgh Coal Conference, Pittsburgh, PA, September 2002. 

Among the metal oxides, calcium-based sorbents have been extensively investigated. The CCR process, which uses the reengineered limestone sorbent has efficiently and economically shown to capture C02 at 600-700°C. Although limestone sorbent is inexpensive, its effective sorption capacity is generally low due to its small surface area and pore sizes (-30% conversion). Hence, the modification of limestone sorbent to form calcium-based sorbents possessing mesopores has been the main focus of the development of CCR process. The conversion of the engineered calcium-based sorbents in carbonation reaction is >90%. 

A high partial pressure of steam is used to hydrate the CaO so that the exothermic reactions of carbonation supply a sufficient amount of energy for the endothermic gasification reaction. The calcium-based sorbent used in the HyPr-Ring process is either CaO or CaO/Ca(OH)2. 

The heat integration of this configuration includes the utilization of the heat generated from the combustion of calcium sulfide in the first chemical loop in the regeneration of the calcium-based sorbent in the second chemical loop (Andrus et al., 2005). The output gas... 

A. Minta, J.P.Y. Kao, R.Y. Tsien, Fluorescent indicators for cytosolic calcium based on rhodamine and fluorescein chromophores J. Biol. Chem 1989,264, 8171-8178. 

CALCIUM-BASED BIOMINERALS CALCIUM CARBONATES IN ASCIDIANS AND MOLLUSCS... 

Table 5 Composition of Ammonia, Sodium, Magnesium, and Calcium Base Sulfite Pulping Liquors...

Parameter Ammonia base mill Sodium base mill Magnesium base mill Calcium base mill ... 

Zhong Z, Dijkstra PJ, Birg C, Westerhausen M, Feijen J (2001) A novel and versatile calcium-based initiator system for the ring-opening polymerization of cyclic esters. Macromolecules 34 3863-3868... 

Ammonia and ammonium persulfate can also be used as reagents (21). However, as pointed out by Nimz (48) and other authors, owing to the non-uniformity of the product, only 15% of urea-formaldehyde and 25% phenol-formaldehyde resin binder may be replaced by calcium base spent sulfite liquors. 

C02. Unfortunately, S02 is less soluble (and hence less easily removed by scrubbing) in slightly acid solutions, so that it is extremely difficult in practice to operate a calcium-bascd system in such a manner that SO2 removal is maximized while the quantities of calcium chemicals are minimized in order to approach stoichiometric conditions. As calcium-based slurry systems are usually operated at pH 6-10, disposal of the very large masses of used slurry presents a major problem. A typical power station using a caldnm-based SO2-removal slurry system will produce several hundred tons of spent slurry per day. A further disadvantage of lime or limestone systems is their marked tendency to precipitate insoluble calcium salts inside the scrubber. Unless the scale is removed, the scrubber shortly becomes inoperable. 

The gas-solid carbonation of calcium-based materials is being investigated for the separation and concentration of C02 using calcium oxide/calcium carbonate car-bonation/calcination cycles (e.g., Ref. [43]), but not for the production of valuable carbonate materials. 

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