Hydration additives

The Dravo hydrate addition at low temperature process involves a two-step injection of water and dry sorbent in a rectangular 19.8-m duct having a cross section of 2 m. In one step water is injected through atomization nozzles to cool the flue gas from 150°C to approximately a 15°C approach to adiabatic saturation. The other step involves the dry injection of hydrated lime, either downstream or upstream of the humidifica tion nozzles. Typical SO2 removals were 50—60% at a Ca S ratio of 2. 

A hydrate is a compound that contains water, rather loosely bound. Usually mild heating of the compound can drive off this water of hydration. Addition of water to the anhydrous salt reforms the hydrate (reversible loss/gain of water)... 

HALT [Hydrate addition at low temperature] A flue-gas desulfurization process in which lime slurry is injected into the combustion gases after they have been cooled in the heat exchanger. Developed in Canada in the mid-1970s. 

The sequence continues with hydration, addition of water, to produce malate, which contains an oxidizable CHOH group. Oxidation involves NAD+,... 

Pteridines also undergo nucleophilic addition reactions particularly easily, including covalent hydration, addition of bisulfite and others. 

The hydroxides may also contain water of hydration additionally present may be some red-brown hematite (Fe2C>3), gray-black iron carbonate (FeCC>3), plus copper oxide, silicates, etc. 

II. PROTON AS AN ELECTROPHILE A. Hydration, Addition of ROH and Related Reactions... 

Several deuterium isotopic effects are found in solid hydrates, additionally to the frequency shifts on deuteration due to the mass ratio (earlier discussed. Sects. 4.2.6, 4.3, 4.4, 4.5). These isotopic effects are caused by the different vibrational zero point energies, the different tunnelling probabilities, and the differently strong H-bonds of hydrates and deuterohydrates, i.e, stronger bonds for OH A than for OD A interactions . ... 

Hydration. Addition of water or the elements of water (i.e., H and OH) to a molecular entity... 

Pore ice plays a particular role for the self-preservation effect in frozen soils Initial hydrate preservation apparently is helped by frozen pore water (not transformed into hydrate). Additional ice formation in the form of a film on the surface of gas-hydrate forming due to hydrate surface dissociation is expected to take place upon gas pressure release. Thus in the sample with 7% of montmorillonite particles (Win=17%), pore hydrate showed a higher stability after pressure release as a consequence of the greater ice content due to the freezing of remaining pore water (Figure 4).Our results clearly indicate that the hydrate content decreases on the expense of an increases of ice (Figure 5). 

Hydration Addition of H 0 or a compound containing active hydrogen, such as NHj,... 

Figure 293. Effects of the amount of hydrate addition on acid gas removal (a) hydrogen chloride (b) sulfur dioxide...

Hydration Addition of the components of water to ti double bond. 

Problem 13.13. We have described acid-catalyzed dehydration (loss of water) of an alcohol to yield an alkene. However, Sec. 12.6.1 described the opposite reaction—acid-catalyzed hydration (addition of water) of an alkene to yield an alcohol. Which is correct ... 

In the case of salts which form hydrates, additionally the water activity has to be taken into account in the solubility product ... 

The hydroxyl radical reacts prefererrtially with forrr carbon centres of gtrartine, thereby generating C2-OH, C4-OH, C5-OH, and C8-OH radical adduct intermediates [59, 74, 78]. The formation of the C8-OH radical adduct is also possible from the C4-OH and C5-OH radical adducts by subsequent dehydration and hydration. It has been shown that dehydration (ehmination of OH") of C4-OH and C5-OH radical adducts generates gtranine radical cation (G ), which upon hydration (addition of OH ) at the C8 position rrltimately yields C8-OH neutral radical irrtermediate (Fig. 3.2) [115]. 

Figure 1 illustrates the effect of NaCl concentration on intinsic viscosities for copolymers of series I with incrementally increasing composition of sulfobetaine mer units. Copolymers with 10,26, and 38 mole percent of 5 (MQ, t 26. and 1-38) are soluble in deionized water and show increases in viscosity across the NaCl concentration range. I-IO and 1-28 may be aggregated (multimers) in deionized water, explaining the initial decrease upon addition of salt. The homopolymer of 5 (MOO) and copolymers MZ and h69 are insoluble in deionized water and require a critical concentration of NaCl for dissolution. In deionized water, the intramolecular dipole-dipole interactions in these copolymers dominate, allowing little hydration. Addition of electrolyte induces the globule-to-random coil transition typical of polyampholyte hydration. 

As has been seen, refluxing thionyl chloride reacts with water and may be used to prepare anhydrous metal chlorides from the hydrates. Additionally, it is a suitable solvent for the preparation of the chloro anions of metals ... 

Dehydration and Hydration—Addition or removal of water from a compound may be accomplished by a catalyst. Dehydration may occur as an independent reaction or as a heterogeneous reaction such as the condensation of an alcohol with ammonia, or the formation of esters fi m alcohols and acids. Alcohols can be dehydrated to form olefins or ethers. Other dehydration reactions are glycerine to acrolein and acetic acid to acid anhydride. Olefins can be condensed with water to form ethers, aldehydes, ketones and alcohols. The hydration reactions are governed by pressure, temperature, and the mole ratio of reactants. High pressures are occasionally necessary to counteract dehydration tendency and promote hydration. 

Water deprotonates the intermediate, giving the neutral hydrate addition product and regenerating the acid catalyst H30". ... 

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