Health Standards oxygen containing


From a bulk chemical standpoint, coking coals may be considered to consist of irregular macromolecules that are nearly two-dimensional and are held together by noncovalent bonds. Up to 80% of the carbon is hydroaromatic or aromatic. This percentage of aromatic molecules, versus aUphatic ones, increases with coal rank. The aromatics are of a condensed angular ring stmcture and are often connected together via aUphatic or ether bridges. These linked rings form chains of molecules along which exist short methyl, ethyl, or hydroxyl side chains. These chains may also contain other elements such as oxygen and sulfur. Coals having lower rank than about high volatile A are generally considered noncoking in that the individual coal particles only weakly, or not at all, fuse together under standard coking conditions. Lower rank coals have a lower aromaticity to the point that most of the carbonization decomposition products consist of low molecular-weight hydrocarbons that are gaseous, thus Httle or no plastic material is generated. Coals higher in rank than low volatile are similarly viewed because their highly aromatic molecules are strongly cross-linked, as a result of the coaUfication process, which prevents generation of much plastic behavior during coking.  [c.244]


See pages that mention the term Health Standards oxygen containing : [c.246]   
Pressure safety design practices for refinery and chemical operations (1998) -- [ c.0 ]