Calcium-based chemicals

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

Where a softener has not been provided, a higher volume of sludge can be expected in the BW. Typically, the calcium precipitates either as insoluble carbonate scale or as phosphate sludge except where a chelant-based chemical treatment program is employed (which is unlikely in smaller boiler plants) or when an all-polymer program is employed. 

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... 

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 development of new families of high-stress tolerant, polymer-phosphonate-based chemical inhibitor programs, that now permit operators of small cooling systems to run at high cycles and alkalinity, with no sulfuric acid, has almost eliminated the risk of accidental calcium sulfate deposition in these systems. 

Calcium Cyanamide (H2N-CN) is used as a fertilizer, herbicide, insecticide, a steel-making additive and an ore processing material. It can also be used to make thiourea, guanidine and ferrocyanides142. SKW Chemicals in Germany (now part of Degussa) claims to be the world leader in production of cyanamide and cyanamide-based chemical intermediates. 

Because there is such a wide selection available, rational choice of the necessary excipients and their concentration is required. Consideration must also be given to cost, reliability, availability, and international acceptability. Although generally considered inert, formulation incompatibility of excipients is also necessary. Lactose, for example, can react with primary and secondary amines via its aldehyde group by Maillaird condensation reaction [6], and calcium carbonate is incompatible with acids due to acid-base chemical reaction and with tetracyclines due to complexation. Additionally, excipients can contribute to the instability of the active substance through moisture distribution. 

Calcium carbide (CaC2), which can be produced by thermal reaction of calcium oxide with coke, is not only the basis for acetylene and acetylene-based chemicals (however with decreasing importance due to the strong competition from crude oil and oil products), but also the basis for calcium cyanamide (CaNC = N) (Langhammer 2002). 

Your bones need calcium to stay strong because they are made of a calcium-based substance called calcium hydroxylapatite, with the chemical formula Ca5(P04)3(0H). It is recommended that people between the ages of 18-50 consume about 1000 milligrams of ctdcium per day, while older people should consume 1200-1500 milligrams of calcium each day. 

Although a feedstock, or a particular feedstock source, is initially taken up because it is produced in excess or is even a waste product, its success can result in the need to manufacture it specially for that process, thereby losing the rationale for its original adoption. One can see this progression at work with coal-tar (in particular phenol ) and synthetic dyes, with coke-based ammonia and the Solvay process, with calcium carbide and acetylene-based chemicals, and, more recently, with refinery gases and petrochemicals. Conversely, butanol became such a major by-product of butadiene production that I.G. could only sell a quarter of it by 1943. ... 

Sorbent injection technology seems to have the highest potential to remove both elemental and oxidized mercury from the flue gas (Yang et al., 2007). Different sorbents such as activated carbon, chemically treated sorbents and coal additives, calcium-based sorbents, petroleum coke, zeolites, fly ash, other chemically treated carbons or carbon substitutes, etc., are injected into the upstream of either an ESP or a fabric filter baghouse to control mercury emissions (Pavlish et al., 2003 Yang et al, 2007). The cost of this process is low-to-moderate and separate injection systems may be required (Pavlish et al., 2003). 

Weerasooriya, U., Aeschbacher, C. L., Leach, B. E., Lin, J. and Robertson, D. T., Process for alkoxylation of esters and products produced therefrom using a calcium-based catalyst to react a lower alkyl oxide and a methyl ester of a fatty acid to obtain a product having a narrow weight distribution, US Patent 5220 046, to Vista Chemical Company (1993) Chem. Abstr., 120, 57218. 

Garcfa-Labiano, F., Abad, A., De Diego, L. et al. (2002) Calcination of calcium-based sorbents at pressure in a broad range of CO2 concentrations. Chemical Engineering Science, 57, 2381-2393. 

R. J. P. Williams points out that several different types of mollusks developed calcium-based shells at the same time, like widely dispersed inventors filing simultaneous, identical patents. Overall, calcification evolved at least 28 times in separate species. Something was in the air (or rather in the water) that allowed this season of chemical innovation. 1 propose that this something was calcium itself, released from the rock by weathering, assisted in binding by oxygen. 

Several different chemical classes of additives are used for thermal stabilization of PVC. These include divalent lead compounds, tin and antimony based chemicals, and mixed compounds of cadmium/ barium, calcium/zinc, and many others. In general, the lead based thermal stabilizers are used in electrical applications, the tin based ones are used for external uses in siding and other extruded shapes, and mixed compounds are used in plastisols and injection molded parts. 

L. Shen, M. Zheng, J. Xiao, R. Xiao, A mechanistic investigation of a calcium-based oxygen carrier for chemical looping combustion. Combust. Flame 154, 489-506 (2008)... 

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