Tannins chemistry

Here, the use of inhibitor formulations having a less dramatic effect on TDS (such as certain tannins) may be extremely beneficial. Formulations are available that are based on tannin chemistry and contain blends that act as oxygen scavengers and metal passivators, with additional sludge dispersant and antifoam properties. 

Although tannins are almost always formulated as a blend of raw materials, some knowledge of tannin chemistry is required because certain tannin constituents are useless in BW formulations and others lack... 

Tannin chemistry is extremely complex, but the individual components may be classified in two primary groups ... 

NOTE Tannin chemistry has been used very successfully for many years in Africa and in Central and South America, in sugar refinery boilers operating at 650 psig and higher, without any measurable breakdown in performance or detectable contamination of steam from volatiles. 

Under poor operational conditions, tannin chemistry is a particularly forgiving form of internal treatment because it tolerates FW with significant variations in quality. It is capable of delivering clean, corrosion-free waterside surfaces in many types of boilers, despite low FW temperatures, high oxygen levels, and hardness ingress. It is especially suitable for use in smaller facilities that do not have the benefit of full-time, trained operators, and under on-off, batch process, or permanent low-fire circumstances. 

Tannin chemistry is complex and tannin blends (composed of singletree species tannins mixed together) offer a number of useful water treatment functions. Apart from oxygen-scavenging abilities, they act as passivating agents, film-formers, sequestrants, and polymeric sludge dispersants (for more details, see Section 10.3). 

KAH, 1786, vii, 30 V, 306 Nierenstein, Incunabula of Tannin Chemistry, 1932, 3 this was Scheele s last published research, but Calm s notes show that Scheele s work on gaUfc and pyrogallic acids goes back to the earliest period, about 1770 VI, 37,40. 

Nierenstein M 1932 Incunabula of tannin chemistry. Edward Arnold London, 116... 

Studies of the reactions of flavan-3-ols and particularly those of catechin have been central to the elucidation of the structure and development of uses for the condensed tannins. This work, initiated by Freudenberg and his colleagues at Heidelberg in the 1920s [see Weinges et al. (377) for a thorough review], continues to be an important aspect of condensed tannin chemistry. A wide range of electrophilic aromatic substitution reactions has been examined to obtain definitive evidence for the location of substitution (i.e. C-6 or C-8) of proanthocyanidins and to establish the influence of steric hindrance on the relative reactivity of these nucleophilic centers in flavan-3-ols. 

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